The Amazing World of Gumball - Season 4

After being framed for feeding coffee to the squirrels in the park, Gumball proclaims that Mrs Robinson is pure evil. Darwin tells him that there's no such thing as pure evil, and sets out to prove that Mrs Robinson wasn't born evil, she just became that way because of a trauma in her past. But when he learns the true darkness of her nature, he decides she deserves her grand comeuppance.