Future Mr. Ross from Regular Show: The Movie attempted to destroy all of space, time, and existence…OVER LOSING A GODDAMN VOLLEYBALL GAME.

And Big Jack Horner

Takaaki Kakinuma locking up Shinichi Gotou (the main character) for 10 years because when they were in elementary school, Shinchi was moved to tears when Takaaki sang.

Evelyn Sharp.

@Mccue What was her reason for becoming evil ? Just curious. Everyone cited the motivations.

Shadow the Hedgehog from Sonic Boom tried to destroy the whole universe just for falling into Dr. Eggman's petty trick

Finding out that Oliver was the Hood and disregarding the fact that Prometheus was the one killing innocent people.

Rob from Tawog trying to destroy Gumball and Darwin because they didn't notice him in the void and can't even remember his name is pretty petty to me.

Aldrich Killian.

Reverse Flash, he is mad at Barry(The Flash) for and I shit you not having a better life than him and this man has gone out of his way time traveling and rewriting timelines to try and ruin Barry's life.