From Zero to Nightmare

A scenario where the said hero turned to the dark side in this way often became shocking events for either viewers, heroes, or other people that learned about this. Reason of this mainly because the said hero always looked down upon, their existence was ignored, and/or 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) no matter what kind of good/heroic efforts that the hero did for others' acknowledgement. Once this individual turned to the dark side, they became feared by many people, includes heroes that faced them. Examples may include various incarnations of the Frankenstein's Monster along with Asriel Dreemurr from Undertale and Gil Yepes from The Prodigies.