MVCI X1 Sigma
Sigma in Marvel vs Capcom
"It's not over yet, X! The battle! The angst! The destruction! I will make you understand the true potential of Reploids!"
―Sigma, [Mega Man Maverick Hunter X]

Sigma (シグマ Shiguma?), formerly referred to as "Commander Sigma", is the main antagonist of the Mega Man X series. He serves as the final boss in all X series games except Mega Man X: Command Mission (where he makes no appearances) and Mega Man X8 (appearing as the final boss if the game is played on easy, and as the penultimate boss if the game is set to normal or hard difficulty, since Lumine is fought on normal or hard).

The first Reploid created by Dr. Cain, Sigma was considered the finest of the Reploids and was the first leader of the Maverick Hunters; peace-keeping Reploids who defend humans against their renegade counterparts. Although he was once honorable, Sigma unexpectedly goes Maverick in the beginning of Mega Man X and rebels against humankind. He defects to the Mavericks and assumes the role of their leader. Under Sigma's command, the Mavericks grow into a legion dedicated to the extermination of the human race. Sigma instigates many of the destructive Maverick Wars, with the Maverick Hunters existing to crush Sigma and his minions.

Although he has been destroyed countless times, Sigma's programming always survives and builds himself a new form, ready to menace the world once again. It is implied that he grows more insidious and vengeful with each transformation, with each successive plan becoming more and more desperate and aggressive. His primary enemies are X, Zero, and more recently, Axl.


Before Mega Man X

As the former leader of the Maverick Hunters, Sigma was originally the most advanced Reploid of his time. Dr. Cain implanted the latest circuitry designs into Sigma, which were theoretically supposed to prevent him from going Maverick. He was placed in charge of the 17th Elite Unit of the Maverick Hunters, and led them to victory multiple times.

One day, the Maverick Hunters received reports of an overwhelmingly powerful "Red Maverick" that has destroyed an entire squadron of Hunters (the Gamma unit). While investigating, Sigma, along with his unit, tracked it down to an abandoned laboratory. Sigma then left to confront it alone, in order to prevent other Reploids' deaths at the hands of the Maverick. It is here that Sigma encountered Zero, the last product of Dr. Wily. Zero, having suffered a programming flaw from his creation, was uncontrollable, unleashing wanton destruction wherever he went. Sigma was beaten badly by the maddened Zero, but managed to smash the energy crystal in Zero's helmet. The fight, due to taking place in close proximity to Zero's capsule, which was leaking trace amounts of the Maverick Virus, and the damage they already sustained in the battle, transferred the Maverick Virus directly into Sigma and Zero, infecting them. Zero lost consciousness, and Sigma limped away from the battle, ordering his men to take the body of Zero back for study. The virus had different effects on them: Although the virus corrected the flawed programming in Zero, it began to mutate and adapt to Sigma's own programming, eventually fusing entirely with his mind to form the Sigma Virus, which allowed him to manipulate and control Reploids, bending them to his will. After this, he began to feel that humanity was keeping Reploid potential down, and decided to revolt against humanity.

Mega Man X/Maverick Hunter X

Sigma's advanced circuitry seems to do its job, as he seemingly remains stable for months after the lab incident. He gradually succumbs to the virus inside of him and grows more volatile. Without warning, he leads a mass revolt among the Reploids, declaring total war on humanity, which is seen depicted in The Day of Σ. Many Maverick Hunters follow Sigma out of loyalty, leaving Zero, who by this time was reformed and had become a powerful Maverick Hunter, in charge of the organization. Mega Man X, the last creation of Dr. Light and the base model for every Reploid, decides to join Zero as thanks for saving his life. X and Zero battle through the Maverick regime, and it is X who finally destroys Sigma, who laments X's decision for siding with humanity, feeling that Reploids would have prospered without humanity holding them back. But, though his physical body is scrapped, Sigma's "soul" (the Virus) survives. After the end credits roll, Sigma's face appears on a blue monitor and warns X that he will be back.

Mega Man X2

Just as he promised he would, Sigma returns and assumes leadership of his Maverick forces. He gains a new body with the help of the X-Hunters, a trio of vengeful Mavericks who worship him, and becomes "Neo Sigma". He also oversees the "Unification" plot, which focuses on capturing and re-assembling the remains of Zero, whom he plans to reprogram to kill Mega Man X. But, since X managed to recover all of Zero's remains from the X-Hunters, Sigma was forced to make a copy of Zero's body that was not unlike Zero's Black Zero form; however, Zero arrives and destroys it completely before it could battle with X. Sigma then announces that he "knows Zero's secret", and that he's destined to serve him. It's unknown what exactly this secret is, but the dialogue suggests that it has something to do with Zero being created by Dr. Wily, and the possible origins of the Maverick Virus as Sigma calls him "the last of the Doctor's creations ". Sigma attacks in his latest form, armed with clawed knuckles, but X thwarts his plans and destroys him again. This marks the first time Sigma's viral form is seen, as the final boss of the game. Zero is then restored to his rightful place in the Maverick Hunters, and is given command of his own Special 0 Unit.

Mega Man Xtreme

Sigma uses a hacker named Techno to hack into the Mother Computer of the Maverick Hunter base. Noticeably more confident than previous times, Sigma taunts X after he's beaten the first time and even calls his defeat at the end of Normal Mode merely a retreat. It's only when he's defeated on Hard Mode that he seems to succumb to X. However, he implies in the ending that he'll return as long as not only mavericks still exist, but also as long as humanity retains evil minds.

Mega Man X3

Sigma resumes his threat when he infects the Reploid scientist Dr. Doppler, who has developed a revolutionary new anti-virus to repel Sigma's influence. Sigma uses him to stage a revolt in Dopple Town, a Utopian city established on the principles of peace. Once Doppler is unmasked as a pawn, Sigma emerges in a heavily-armored form, "Kaiser Sigma" (カイザーシグマ Kaizā Shiguma?). After his defeat for the third time, Sigma's "soul" appears in the form of a wire-frame head, which is identical to the Sigma Virus', and threatens to possess X's body to replace its own. After chasing X through the flaming wreckage of the base, Sigma finally corners him. If Zero did not end up critically wounded at any point during the game, which would have forced him to leave the war to X as he was repaired, Zero appears and utilizes the anti-Virus created by Doppler to erase Sigma for the time being. If Zero did end up critically wounded, including the method by which X receives the Z-Saber, Doppler uses the anti-Virus and sacrifices himself to destroy Sigma's programming.

Mega Man Xtreme 2

In Mega Man Xtreme 2, Sigma appears in Extreme Mode after the defeat of the Soul Erasers Berkana or Gareth (depending on if the player is X or Zero), where it's revealed he was behind the Erasure incident. In a rare instance, he's pleased that X defeated Berkana, claiming she went too far in her greed.

Mega Man X4

Sigma was thought to be suppressed forever after Zero distributed the anti-virus created by Doppler, but he still manages to return. In the introduction of the game, Sigma, assuming a Grim Reaper-like appearance, acts as a double-agent between the Mavericks and Repliforce, a benevolent squadron of Reploids who assist the Maverick Hunters. Sigma's true motive is to conspire against Repliforce and turn it into a rogue enemy. He stages the bombing of the airborne metropolis Sky Lagoon, which plummets to the ground in the opening of the game.

With in-fighting between the Hunters and Repliforce threatening to destroy them both, Sigma increases his influence over the paranoid General of Repliforce. The General, an outspoken advocate of Reploid independence, loses all faith in peace and prepares a satellite laser attack on all humans, which is Sigma's real intention. Fortunately, Mega Man X storms the space weapon and stops the General before he can turn its sights on Earth. In the end, Sigma is revealed as the true mastermind and battles X himself, armed with a new body and a scythe. Despite his defeat at X's hands, he succeeds in part by destroying Repliforce. In order to ensure both sides of the war were manipulated, he also had one of his agents, Double, infiltrate the ranks of the Maverick Hunters, and also seduced Magma Dragoon with the concept of power and a chance to fight X/Zero in exchange for instigating the war. He also had Cyber Peacock and Split Mushroom fight against X/Zero to test their power and capabilities. Eventually, he had Double fight X when he infiltrated the Final Weapon, and also ordered him to kill some members of the 17th Unit of the Maverick Hunters as their presence risked compromising Sigma's plans.

Mega Man X5

It is some time before Sigma resurfaces again. During his absence, Sigma traced Zero's origins to Dr. Wily, and hatches a plot to unlock Zero's "true" power — the Zero Virus — inside him. Sigma also adapts his programming to completely overwhelm the anti-virus; the Sigma Virus quickly begins spreading everywhere, turning peaceful machines and Maverick Hunters alike into violent servants of Sigma. The Maverick leader also enlists the help of a Reploid bounty hunter named Dynamo to crash the orbiting space colony Eurasia into the Earth, as well as to hinder the Hunters' plans of stopping the collision.

Sigma's ultimate goal is to mix his own viral code, which is spread across Earth, with the original Zero Virus, and become all-powerful. Sigma hesitates to kill Zero, intending to make him "remember" who he is and revert to his original, intended programming. He fails in this endeavor, and both X and Zero defeat Sigma's new "Final Sigma W" body (which has been possibly powered and/or developed by Dr. Wily, although this may just be speculation). The speculation comes from this quote of Sigma:

"Here I am. You can challenge me at anytime. I have delightful news. I've recently acquired a new partner. He has been very supportive. He seems to have created quite a few robots. And he gave me the toughest body that you will ever see. You got here sooner than I expected, so it is not yet complete... is enough to defeat you... He is an excellent partner... I believe you two know each other... In fact, he used to be a comrade of yours. He was very persistent about you... and that makes him very helpful to me. You see X, there is someone other than me...who hates you... Now feel our combined rage and die! ...But not before suffering horribly, hahaha! ...Goodbye, X!"

In the aftermath of the battle, Zero's severed torso lies dormant on the floor. X picks Zero up and tries to get him to respond. The remains of Sigma's head lying nearby suddenly become active and fire an energy laser directly at X and Zero, hitting both of them in the chest. As Zero's body falls from X's grasp, he manages to fire one last blast from his Z-Buster and finishes Sigma. X is critically wounded in the battle, both from the battle itself and Sigma's final attack (the force of the laser being so strong that it ripped through his body and destroyed his entire lower half and arms), but he is eventually repaired (the cutscene suggesting that it may have been by Dr. Light) and returned to the Hunters.

Mega Man X6

Three weeks pass as the human population moves underground to survive the devastation and pollution left by Sigma's last attack. Sigma himself is quickly resurrected by a renegade Reploid scientist, Gate, who was angry at the scientific community for rejecting his advanced Reploid designs. Gate becomes a Maverick after coming into contact with a piece of rubble that contains signatures of the Zero Virus. He then uncovers Sigma's remains, and proceeds to rebuild him. However, due to the stress of spreading the Sigma Virus during Mega Man X5's "Colony Incident", Sigma's programming is damaged beyond what Gate can repair, and he is reduced to a half-conscious and barely-functioning wreck of his former self. Gate's work on Sigma's new body is unfinished by the time X or Zero confronts him at the end of the game. Although it seems as though Gate rebuilt Sigma merely as a backup plan to further his own goals, Sigma is quick to finish him off after X or Zero finally defeat Gate in battle, stating: "Oh please, I did not die, nor did I need your help. Now get lost!". Along with his final lines before being destroyed, this is the only instance in Mega Man X6 in which Sigma speaks incoherently. He seems to remember little more than his rage toward X and Zero and speaks in a garbled voice.

Mega Man X7

Sigma reappears yet again, under the alias of "The Professor", to manipulate the Maverick hunting organization known as Red Alert. His plan was to use a mysterious young Reploid named Axl to copy the D.N.A. signatures of X and Zero and implant them into destructive war machines. The plan fails when Axl flees Red Alert and seeks asylum with the Maverick Hunters.

This prompts Sigma to find a way to bring Axl back into the Red Alert group. He secretly infected the eight Red Alert generals, blackmailing Red into following his orders and causing Maverick uprisings to draw in the Hunters' attention so that they could infiltrate the Crimson Palace. There, the Hunters confront Red, and upon being defeated he regrets being used by "The Professor" and sets part of the building to self-destruct, seemingly killing himself in the process.

Afterwards, the Hunters confronted Sigma, and once defeated, a reborn Sigma (who appears similar to his first form in Mega Man X6) punches Axl through a wall before vowing to X and Zero to again return in a new body.

Red, who had been defeated earlier and presumably killed, reappears, and Sigma attempts to possess him. Red is then revealed to be Axl taking on Red's form, who then proceeds to blast Sigma out of a window.

Unusually for most games in the X series, Sigma is not actually identified by name, even when he reveals himself.

Mega Man X8

Sigma's next plot was very complex, and it wasn't even him behind the entire scheme. It turned out that Axl was a prototype for a new generation of Reploids. These next generation Reploids possessed advanced copy abilities, and Alia discovered that the copy chips bore copies of Sigma's program among other powerful Reploids. Sigma instigated a new Maverick revolt with these new Reploids as the humans were evacuating Earth in hopes of finding a new home on the Moon. However, the revolt was stopped, Sigma was completely devastated, and the real mastermind, Lumine, the manager of the Jakob Project, was revealed and beaten. Before his death, Lumine made a startling claim: according to Lumine, Sigma was destroyed for good and not returning.

It is believed that the reason Sigma would not regenerate within another body after his final defeat is that he was on the Moon, where due to the lack of available bodies to possess, the virus might have weakened in the vastness of space and got completely deleted (although he was also defeated in space in Mega Man X4, however, that time it was on a large satellite; and the fact that Sigma didn't seem frustrated about this defeat implying that he could escape). There was also a lack of spare bodies, and his last body was hardly finished. However, his DNA is included in every copy chip of all the next generation Reploids so, technically, all New Generation Reploids are "infected" with the Sigma Virus, and possibly Lumine as well; meaning Sigma may return one day.


Although Sigma has taken many drastically diverse forms throughout the X series, his humanoid design remains fairly consistent. He appears as a tall, intimidating humanoid Reploid and being one of the few in the series to not wear a helmet or headpiece of any kind, showing off his bald cranium and lack of eyebrows. His facial features suggest the appearance of a middle-aged man, with a large square chin and small, blue eyes, and a small red jewel embedded in his forehead. In addition to having a fair complexion, his face also features a pair of scar-like marks run down both eyes, resembling a snake bite. How he got these scars vary: either from his first scuffle with a Maverick Zero, depicted in an animated flashback in Mega Man X4, where he was severely damaged, as shown in The Day of Σ, where X in a fit of rage, burned the scars into Sigma's face with his bare hand, or in the manga version of the story where he burned the scars into his face with his own hands as a sign of rebellion. However, no matter what form he takes, Sigma always retains his head's initial appearance, making him easily recognizable.


Sigma was originally an honorable and selfless leader of the Maverick Hunters, but after his corruption, he became a power-hungry tyrant, although even then, he also genuinely believed that he was doing what was in the best interests of the Reploids. He typically looks down on others and does not hesitate to kill the weak, laughing maniacally at their expense. His previous "protection through aggression" philosophy has mutated following his infection into a huge Darwinism complex, believing that anything that is too weak to progress should be annihilated, a la natural selection. Following his defeat, his further descent into madness transcended death, trying to hold onto any grip in the living world, in any form possible, consumed by the lingering thought of killing X. Amidst his madness, Sigma is a calculating and intelligent individual, and on more than one occasion, turned allies of X and Zero against them, and instigated many of the most destructive events of the Maverick Wars, including the Earth Crisis. Sigma is obsessed with Reploid evolution and superiority, and believes humanity has run its course. Despite his hatred for X and Zero, Sigma once believed they were the future of all Reploids, and would lead them all into a new age. In addition, he also credited X's dedication to justice, as well as his being infected with Zero's virus, as being his primary motivation in his going Maverick, including what ultimately turned out to be his final battle on the Moon.


As the former leader of the Maverick Hunters, Sigma is a capable military leader, described as possessing overwhelming combat power and strategic intelligence. When he turned Maverick, Sigma remains a charismatic leader, and is revived on many occasions by Reploid and Maverick admirers alike. Due to the virus in his circuits, he can survive seemingly anything and always return for more. He is a very powerful Reploid, and is fond of incorporating himself into battle suits which are vastly larger and more powerful than his "regular" form. Sigma is also a skilled manipulator, managing to turn various Reploids, Maverick Hunters, and Mavericks to his side. In fact, there were few instances in the entire series where Sigma wasn't pulling the strings. Sigma himself is one of the strongest Reploids ever created, due to his original role as leader of the Maverick Hunters. His personal energy has been stated to be too powerful to even get an accurate reading. In addition, Sigma's combat skills and analytical abilities were extensive enough that he was able to wipe out several reploids in an efficient manner, as Zero noted when investigating the crime scenes on the days leading to Sigma's revolt.

Sigma is capable of moving at great speed, often able to move faster than the hero can follow, vanishing from sight. Many of his bodies are also capable of teleportation. Sigma seems to favor saber and beam sword weaponry, often integrating powerful sword combos with his blinding speed or teleportation. On several occasions, he projects energy barriers around himself to block incoming attacks. In nearly every appearance, Sigma is capable of discharging enormous destructive blasts or waves of power capable of covering entire battle areas. Sigma's physical strength is considerable. In his first body, during a conflict with the original Maverick Zero, he was able to effortlessly break through Zero's defenses with a round kick, as well as easily toss Zero through the ceiling with a single hand. He has also demonstrated the ability to scale a skyscraper with a single leap.

Sometime prior to Sigma's first defeat at the hands of Mega Man X, his reploid soul became intermingled with the dangerous Maverick Virus and formed the Sigma Virus. This allowed Sigma's spirit to remain after his body was destroyed, granting him immortality and the ability to return after the destruction of each subsequent body. The Sigma Virus possesses the ability to travel through any material or energy and can manipulate both reploid and organic hosts, even on a planetary scale. Its intangibility allows it to ignore physical assaults and energy attacks, except for those tuned with a Virus Buster to target the Sigma Virus's unique matrix. No solution for the Virus remained ultimately effective during 21XX-22XX, as Sigma demonstrated the ability to adapt to any countermeasure. As the cause of death and suffering for countless innocent lives, Sigma is one of the most dangerous villains in the Classic Mega Man Universe.


Axl (using his copy ability) vs. Sigma.

Street Fighter IV - Secret Sigma Boss Battle

Street Fighter IV - Secret Sigma Boss Battle


  • Interestingly, Sigma was designed by merging a team of three other early villain designs created by Inafune during the early development of the first Mega Man X game. The same designs were later used again as the basis for the X-Hunters in Mega Man X2.[1]
  • His appearance has a close similarity to both M. Bison and Sagat, both of whom are major villains of the Street Fighter series and both of whom were designed by Keiji Inafune.
  • During a 2008 question and answer session, Keiji Inafune stated that Sigma (and Zero) represents the idea that nothing is absolute.[2]
  • Sigma (Σ) is the 18th letter of the Greek alphabet, and is used in mathematics to denote series, finite or infinite sums of variables. The Σ symbol is often seen on Mavericks from Sigma's army. Interestingly, the Sigma (Σ) letter was originated from the Phoenician letter Sheen (W), which is similar to the English letter "W".
  • There are three variations on the way Sigma got the scars on his eyes:
  1. Zero damaged Sigma's face when they fought (as shown in an animated cutscene in X4).
  2. X damaged his face in The Day of Σ. Ironically, after Sigma's head merges with the wolf robot in the game, his face resembles his face deformity received against Maverick Zero.
  3. Sigma did it himself after going Maverick in the manga, by using the heat of the "weapon" (his fingers) he used to shoot Kyle to make the scars.
  • Sigma is called "Cigma" in the Mega Man cartoon series.
  • Sigma's viral form from X8 bears a slight resemblance to Abyss (first form) from Marvel vs. Capcom 2.
  • Sigma's normal form in Mega Man X8 is a redesign of his armor from the first Mega Man X.
    • Also, Sigma's "scars" in Mega Man X8 do not really look like scars, rather just lines running down his face.
  • If Sigma's name is entered as the player's name in Mega Man 9, the game will say that it is "inappropriate language", and changes it to "Si**a".
  • Although Sigma is never seen or mentioned in the Mega Man Zero series he does make cameo in the Rockman Zero manga.
  • In Mega Man X8, the copy of Sigma is weak against Dark Mantis' weapon, while the real Sigma is weak against Optic Sunflower's weapon. Both weapons are based on darkness and light, respectively.
  • In the Ruby Spears Mega Man episode, "The Mega X", Mega Man X mentions to Dr.Light that the lightanium is worth billions in the future, which can fund Sigma's rebellion. This creates some confusion as to why Sigma ever needed funds, as he shows to not have any necessity to have funds for anything.
  • Oddly, only the first and third Mega Man X games have official artwork for both of Sigma's forms.
  • In the original Mega Man X, Sigma berates X as he realized why Zero counted on him, while in the remake, he does no such thing, but commends X's ability to finally reach him.
  • While Sigma does not appear directly in Project X Zone at all, he was mentioned briefly by name in Chapter 20, the same chapter X and Zero officially join the party. 
  • In the original Mega Man X, Wolf Sigma has floating hands. In Maverick Hunter X, however, Wolf Sigma has arms and hands.


  1. Mega Man X Official Complete Works, UDON Entertainment Corp. 2009. pg.93. Retrieved on April 8, 2011.
  2. "Some people think he might have been inspired by Sagat from Street Fighter because of his look, but that's not actually the case. Sigma and Zero basically represent the idea that nothing is absolute. Sigma was a powerful leader of the Maverick Hunters but after Zero passed the virus to him, his allegiance changed. Circumstances can change anything, and nothing is absolute." --Keiji Inafune, 2008. Capcom-unity - Inafune-san Answers Your Questions!
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