From Nobody to Nightmare

"Why not? I've been hurt my life."

- Carrie White (about using her psychokinetic powers against those who wronged her) to Sue Snell in Carrie (2013).

Nobody to Nightmare is a TV Trope-popularized villainous event involving a character, either a hero or ordinary good guy whom either harmless/helpless, looked down upon, his/her existence was ignored (like Max Dillon), 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 where they featured at.

How an ordinary good guy become nightmarish villain in this scenario can be either: In either way, when the fateful day where they turned to the dark side comes, they would cause particulary shocking event that horrifies everyone, be it either the hero, audience, and other people whom witnessed such event.
 * Protagonist/other good guys' tragic mistake or other well-intentioned but disastrous acts that resulting them depressed and pushed to the dark side.
 * Result of the Big Bad or other villain's evil acts that intended to either merely ruined their innocence; rewarding the character with violence and cruelty out of prejudice/fear/jealousy/sheer hatred; or more complex instance, corrupted so he/she become their servant/disposable pawns.
 * Feels dissastified with current life/status but choose go for the dark path to improved it.
 * Becoming more and more villainous than he/she previously.

Anime and Manga

 * Naruto:
 * Jinchuurikis: Tend to suffer this due to either prejudice or terrible grudge against Tailed Beasts whom inside them by villagers of the village where they lived at. One of them, Gaara, was not only mistreated due to him a walking prison of Shukaku, but also have his caretaker tried to killed him seemingly under his own father Rasa the Fourth Kazekage that resulting the loss of innocence and become sociopathic killer until other Jinchuuriki Naruto help him return to the good side. Ironically, when Gaara become a Kazekage himself and assumed that his father's attempt murder on him was due to for sake of village, he asked this to the reincarnated Rasa, only to be revealed that the attempt murder proved to be a tragic mistake.
 * Although Naruto himself potentially can become From Nobody to Nightmare due to his mistreatments, an ironic twist occured where one of his tormentor, Mizuki, wind up become one both due to Mizuki himself already evil from start and Naruto finally able to found those whom cared about him. This is apparent in anime filler where he causes massive breakout in prison where he was held and gives Naruto whom attempt to stop him troubles.
 * Tobi: The masked man whom inherited Madara's name that later turns out to be none other than Obito Uchiha, the same kid that spent his childhood failing at everything, pining for Rin, feeling jealous of Kakashi, and pretty much like Naruto that we know today, is now the villain who indirectly killed Naruto's parents (one of which was his own sensei) by taking control of Kurama and unleashing him on Konoha (though in certain point of view, he directly killed both Minato and Kushina as Kurama is merely scapegoat whom tries to prevent himself from being sealed again), took part in the Uchiha massacre, corrupted Nagato and later Sasuke, co-led the aforementioned evil army against the five great powers of the world and was working to unleash Juubi. Little that did he knew that Tobi, along with Madara, was merely pawn of the true apocalyptic being.

Western Cartoons & Animated Films

 * Lotso was once a soft-spoken, gentle, lovable teddy bear who first started out as a Christmas present for Daisy, a young kind-hearted girl who immediately became overjoyed the moment she unwrapped him. Things suddenly take a dramatic turn when on a family trip, as Daisy happily played with her toys including her very special Lotso, she fell asleep after lunch, accidently leaving her toys behind. Lotso and his friends decided to go back home afterwards, but by the time they got there, it turned out Daisy bought another Lotso to compensate for the original one she lost during the trip. Right when Lotso saw this, something snapped inside him that day...It should be noted, that Daisy only bought another Lotso because he symbolized how much she truly loved her original. As pointed out by Woody, it was Lotso who abandoned Daisy to begin with.
 * Tighten: Hal Stewart started out as awkward cameraman with a crush on Roxanne Ritchi, but obtained superpowers via Megamind and became the supervillain Titan, an Omnicidal Maniac who is willing to obliterate an entire city just because Roxanne won't give into his even more disturbing advances.