Superboy-Prime

Superboy-Prime was one of the many variations of Superman in the DC universe but became unhinged following the destruction of his world and become one of the main villains of the Crisis On Infinite Worlds storyline: he had even more power than current Superman and was comparable to the Silver Age Superman in scale of power - making him easily one of the most powerful supervillains in DC comics.

Although a villain Superboy--Prime was also tragic and wasn't evil so much as a very confused and angry person - however he let his pain warp him into a monster and thus had to be stopped in order to save reality from destruction.