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. Once a protagonist or good guy, these villains turn evil due to events in their lives, such as being corupted by another villains, their desire for revenge, a failed love relationship, or even betrayal from the good side to the dark side.
Some Heroes turned to the Dark Side (Fallen Hero for short) can become Complete Monsters to add drama as they are willing to be evil without remorse, redemption or positive qualities at all, such as Zalgo, Shadow Aaron, InJustice, Commander Zonos, and Pepper Satanica.
One such example would be Killing Jack, who was originally a fun loving and kind clown, who slowly became corrupted, and due to his imprisonment, he became emotionless. Another exmaple would be Amethyst Paradinight, who was once a sweet, kind and gentle girl who do not wish to harm anyone and was frightened of the thought of killing, and focused on defensive powers. She even hesitated in killing her own family who had formerly abused her and even gave her away to be tortured and experimented on, until they killed her only friend in front of her, casuing her to finally snap.
- From Nobody to Nightmare: Scenario where the said individual turned to the dark side in this way often became a shocking events for either viewers, heroes, or other people that learned about this. Reason of this mainly because the said individual are used to be either harmless/helpless, looked down upon, his/her existence was ignored, and worse, considered as an outcast or an individual that often being abused by other people that dislikes/hate them, either the Big Bad or merely minor villains in the story. Once this individual turned to the dark side, they became feared by many people, includes heroes that facing them.
- Not good with Rejection: The said individual may once, an acquaintance/love interest of heroes that befriended them prior turned to the dark side. One day, the said individual either made an offer or confessing love to the said hero, in which both cases, the hero rejected it. The individual then unable to cope with this, and thus, decided turned to the dark side. The worse the hero reject the individual, more farther that individual turned to the dark side.
- Being an Extremist: Scenario where 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.
- From Victim to Villain: These characters were once people who tried to be friendly and do good, but were rewarded with violence and cruelty by society. Often they were bully victims. And eventually they were pushed so hard the finally snapped and now seek revenge on the very society that shunned and hated them. Despite their tragic nature, very few of these characters actually are redeemable 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.
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.
Please note that a character has to have been established as a hero before turning evil. Morally neutral characters - ala "average joes" or characters initially uninvolved with any side of the conflict - do not count. False Heroes - if they never were good - do not count either.