Many heroes walk a thin line between good and evil; indeed, many heroes have fallen into despair, rage or even madness, and once proud heroes descend further into the path of evil, often fighting against people they once protected or fought alongside.

Originally protagonists or forces of good, these villains turn evil due to events in their lives, such as being corrupted by another villain (i.e. convinced by villain's arguments), their desire for revenge, a failed love relationship, betrayal from the good side to the dark side, or any other unresolved traumatic experience in which they question whether or not the good side is worth fighting for.

A Fallen Hero - or hero turned to the dark side - is usually the end result of a protagonist exposed to a Corrupting Influence, Deal Makers, Brainwasher, and occasionally an Extortionist, Blackmailer, or even a Bond Destroyer. However, some heroes may turn for more greedy reasons (i.e. "From Sugar to Excrement" scenario).

In rare situations, some heroes turned to the dark side can become Purely Evil to add drama as they are willing to be evil without any remorse or positive qualities after all. Good examples include Makuta Teridax, Terumi Yuuki, Zamasu and Griffith. However, some of them can still redeem themselves, especially if they were former henchmen who eventually betrayed their masters when they come to realise just how evil they really are, such as Big Baby and Speckles.

There are various scenarios for why these individuals turned to the dark side, though the said individual often to fell onto multiple scenarios altogether:

• From Zero to Nightmare: A scenario where the said hero turned to the dark side in this way often became a shocking event for either viewer, heroes, or other people that found out about this. Reason of this mainly because the said hero always looked down upon, his/her existence was ignored, and/or worse, considered as an outcast or an individual that often being abused by other people that dislike/hate them (either the Big Bad or merely minor villains in the story) no matter what kind of good/heroic efforts that he/she did for others' acknowledgement. Once this individual turned to the dark side, they (usually) became feared by many people, includes heroes that faced them. Good examples of this include Savitar, Dave and various incarnations of Frankenstein's Monster.
  • From Victim to Villain: In this sub-scenario, these characters were once people who tried to be friendly and do good, but were rewarded with injustice and ingratitude by society. Often, they were victims of bullying or abuse, and eventually they were pushed so hard they finally snapped and now seek revenge on the very society or people that shunned and hated them. Despite their tragic nature, very few of these characters actually are redeemable. Not because they are Pure Evil, but because they almost never forgive or forget, and/or are now completely insane and cannot be reasoned with. Often, they enact the exact same cruelty, or even worse cruelty, on their tormentors, and even innocent people, making them no different or even worse than their tormentors. Examples include Lucy and Andrew Detmer both of whom, after being bullied and abused by others, finally went killing sprees, became even worse than their tormentors, and in the end, had to be killed in order to save others.
• Not good with Rejection: A character may have once had an acquaintance or love interest who befriended them prior to their turn to the dark side. One day, the individual either made an offer, confessed their love, or presented a certain proposal to the hero(es) which the hero(es) rejected. The individual, unable to cope with this, thus decided turned to the dark side. Generally, the worse the hero(es) reject(s) the individual, the farther that individual turns to the dark side. Good examples of this include Bill from Kill Bill and Alex Forrest.
• Being an Extremist: A character has well-intentioned goals for the greater good, but their methods and ultimate ends are proven to be very extreme to the point that they become something that is greatly despised, whether by those whom they know, the heroes, or themselves. The said actions may even potentially drive them to the dark side as well, even if most of these characters become Anti-Villains in the process. Good examples of this include Nathaniel Barnes, Renegade Shepard and Damon Gant.
• From Sugar to Excrement: These characters were once highly revered and loved by their peers but turned evil, either by greed, lust or simply because they were "tired" of being good, bringing shock and despair to those who knew them. Examples include Baron Kelvin, Tankor and Yoshihito Kanamori.
  • From Defender of life to Power-Hungry: In this sub-scenario, these heroes originally wanted to protect the lives of their people but eventually come to realize that they can use their powers to destroy anything to get more power than before. Examples may include Megatronus (from Transformers: Robots in Disguise), Zanza and Ultraman Belial. Another example is Elgen Inc., formerly a medical equipment manufacturer that accidentally created electric rats using one of their medical devices and gained control of the world's energy.
• Being Possessed/brainwashed: Once heroic, these characters were either possessed or brainwashed by another villain or corruptive presence, and consequently became villains. However, this is the rarest and most controversial form of a hero turning to the dark side since they did not turn evil by their own free will and essentially had to be programmed into being villainous. Examples may include most of the characters from the Possessed/Brainwashed category, such as Liu Kang from Mortal Kombat X. Most of these characters redeem themselves after snapping out of their current state.

Notes

Please note that a character has to have been established as a hero before turning evil.

• Morally neutral characters (a la "average joes") or characters initially un-involved with any side of the conflict do not count.
• False heroes, if they never were good, do not count either (e.g. Kristoph Gavin, Napoleon of Animal Farm, and Prince Hans from Frozen).
• Note that Tragic villains do NOT automatically mean that they are heroes turned to the dark side. This category is meant for villains who used to actively work for the good side. Also, this kind of hero is the polar opposite of Pure Good heroes that are absolutely incorruptible.
• Also, do not create pages based on this category, as long time heroes who were only briefly fallen or on & off "jerks" (Such as Barnacle Boy who only fell to the dark side over a Silly Meal and called himself Barnacle Man in the Spongebob Squarepants episode Mermaid Man and Barnacle Boy V but then eventually redeemed himself) do not count.

See also

• Fallen Heroes on the The Evil Wiki.
• From Nobody to Nightmare on the The Evil Wiki.
• From Champion to Power Hungry on the The Evil Wiki.