Insanity

Insanity is a recurring theme in the Mega Man franchise. Many characters in the series exhibit symptoms of mania or outright insanity, often seeking to cause great harm or destruction to others or the world in the name of their cause. Though these causes are often meant to do good for either humanity or Reploids, the amount of damage it will inflict heavily outweighs the positive changes, and must be stopped. Some individuals, however, seek revenge for something that happened to them or for someone they have lost. Others, such as Vile, are driven to prove their own self-worth, and go to extreme measures to do so.

Original Mega Man series
Dr. Wily was once a man with good intentions; as shown in Mega Man 11, his original vision was to create something that could turn ordinary robots into superheroes by enhancing their powers. Wily attempted to achieve this with the Double Gear System, but Dr. Light, believing that the Double Gear System was too dangerous, got Wily's research on the Double Gear project cancelled while both doctors were still in university. This angered Wily so severely that he ended his friendship with Light and stormed off to prove the world that he was "right all along." Since then, his worldview grew more and more extreme over time; this, combined with the envy Wily developed from constantly being overshadowed by Light's achievements, eventually drove him to attempt to take over the world countless times, even after being defeated by Mega Man time and time again.

Grenade Man is a sadomasochist; he takes pleasure in both receiving pain and inflicting it on others. This is shown prominently during his battle in Mega Man 8; aside from constantly expressing his desire to crush or destroy Mega Man, he also giggles when hit with his weakness, the Thunder Claw, and enthusiastically shouts "Oh yeah!" when hit by one of his own Flash Bombs. He even exclaims "That felt good!" when he's finally defeated.

Burner Man was tricked by King into believing that there was a bomb inside of him that would explode and destroy him unless he burned down a forest every day. This has led to Burner Man becoming a pyromaniac who takes joy in causing environmental destructuon for the sake of warding off the make-believe threat of self-destruction.

Mega Man X series
Sigma originally had a stable grip on his sanity, but he lost it after he went Maverick and his worldview was warped drastically by the Maverick Virus. After fully succumbing to the virus, Sigma adopted the belief that humans are holding Reploids back and must be destroyed in order for Reploids to continue evolving. Acting on this belief, Sigma has made many attempts to destroy humanity, as well as the Maverick Hunters that oppose him. Prior to his defeat in Mega Man X8, Sigma was able to resurrect himself after each defeat, progressively growing more and more deranged the more times he returned from the dead.

Vile suffers from a short circuit in his electronic brain, causing him to be reckless and needlessly violent. These traits, as well as his lust for revenge against his enemies, are shown prominently in all of his appearances in the series. Even though he was a Maverick Hunter, Vile's aggressive nature got him branded as a Maverick due to how much of a danger he was to himself and everyone around him. When Sigma became a Maverick and initiated a revolution against humanity, Vile joined the movement to prove his strength. He was destroyed by X in Mega Man X, but later rebuilt and upgraded by Dr. Doppler in Mega Man X3. Upon being resurrected by the doctor, Vile found that the only thing he could think of was exacting his revenge on X (additionally, the English SNES manual states that Vile was also infected with the Maverick Virus, which further augmented his insanity), and he broke free from Doppler's control to pursue X on his own, only to be destroyed again. Vile returned once more in Mega Man X8 with the same goal in mind, although this time around he also made comments about creating a new world only for new Reploids, as if he were one of the New Generation Reploids.

Double was shown to have a split personality befitting his two forms. While his rotund first form is shown to be well-mannered and meek, his second form was shown to be very psychotic and sadistic, taking noticeable pleasure in slaughtering his fellow Maverick Hunters upon being ordered to do so by Sigma, and even when defeated by X showed absolutely no remorse for his actions, even claiming that X's gentle and merciful nature would ultimately be the latter's downfall.

Awakened Zero is Zero from the Bad Ending of Mega Man X5. If the player were to fail to stop the Space Colony from crashing, Zero would go Maverick. Even before then, however, largely because of a glitch in his programming, Zero prior to becoming a Maverick Hunter was shown to be deeply erratic and psychotic; during this time, he did not even speak at all, instead only emitting manic laughter and anguished or rage-filled yells.

Gate, similar to Dr. Wily, initially had good intentions behind his actions. However, he ended up betrayed by his colleagues, including future Maverick Hunter Alia (although unwillingly on her part) due to jealousy, which left him embittered. Eventually, due to stumbling upon one of Zero's parts and becoming infected by residual Zero virus DNA, he became megalomaniacal and vengeance-driven, willing to render the nearly destroyed world asunder and even willingly attempted to revive Sigma as a last-ditch effort at revenge.

Zero Nightmare

Copy Sigma largely has the same traits post-infection that his template had, although it's implied his insanity had existed from the start due to his being a New Generation Reploid.

Lumine seemed stable when first encountered, although it was eventually revealed to be an act. Upon dropping his facade, his true nature was shown to be very megalomaniacal and violent, explicitly desiring to depopulate all old-model reploids and humans. While affected to some degree by Sigma's template, he also implies that his insanity was even more severe than Sigma's had ever been. His statement about Sigma merely "helping" his plan along before crushing Sigma's remains also implies that he's treacherous.

Certain Mavericks have suffered from varying degrees of insanity. Crush Crawfish had a glitch in his AI programming that made him unable to tell his friends from his enemies, causing him to become very violent in nature. In Mega Man X5, if the player chose Zero and Eurasia either crashed or was destroyed, Spiral Pegasus is shown to have been driven completely insane by the Maverick Virus; upon encountering Zero, Pegasus doesn't recognize him and calls out to Iris (who had already been killed in Mega Man X4), and then tries to kill Zero. Optic Sunflower appears to suffer from some confusion and forget who he is when confronted by the Maverick Hunters if he's one of the first four Mavericks the player chooses to face; when approached, Sunflower briefly freaks out and starts asking who he is before regaining his senses.

Mega Man Zero series
Dr. Weil, while initially keeping it contained during the Mega Man Zero 3 story proper, was shown to be vengeance-filled, psychotic, and very sadistic. Even prior to being made into a cyborg, he always enjoyed the carnage inflicted onto others during the Elf Wars, as he himself admitted to Zero. He also was shown to be deeply megalomaniacal, as he freely admitted that the only true source of happiness for humans like himself is in dominating over everything forcing everything to work for them, and also strongly implies all humans are like this.

Omega, befitting his title of God of Destruction, is shown to be intensely sadistic and bloodthirsty, constantly causing carnage wherever he went.

Mega Man ZX
Serpent.

Prometheus and Pandora.

Master Albert.

Siarnaq.

Master Thomas.

Mega Man Battle Network series
Lord Wily.

Sean Obihiro.

Speedy Dave.

Anetta.

Dr. Regal.

Mega Man Star Force series
Dr. Vega.

Mega Man cartoon series
Dr. Wily (Ruby-Spears).

MegaMan NT Warrior series
Mr. Wily.

Dr. Regal (anime).

Darkloids.

Domon Atsuki.

Professor (anime).

Mega Man Megamix and Gigamix
Bass (Mega Man Megamix).

Archie Comics
M'egga Man

Sonic Man (Roboticized Master)

Sigma/Archie Comics

Vile/Archie Comics

Rockman X Mega Mission
Σ Limited

Not Mega Man Related
M. Bison

Doctor Eggman

Deadly Six