Mrs. Puff

Mrs. "Poppy" Puff is a normally neutral character in SpongeBob SquarePants. She is SpongeBob boating school teacher, and with each episode, she grows more and more hateful towards him. However, in one of her episode appearances, she played the role as the main antagonist in the season eight episode "Demolition Doofus." After one of SpongeBob failed attempts at driving, she becomes deflated, and very cruel towards SpongeBob. While at the hospital, she sees injured demolition derby drivers and enters SpongeBob in the annual demolition derby. She hoped that he would literally die in said derby. However, much to her displeasure, he survives thanks to his reckless driving, and becomes a star. She then snaps and crosses the moral event horizon by getting into a large monster truck and attempting to murder SpongeBob herself. She then regains her puffing ability, however, by crashing into her boating school. She still acts cruel towards SpongeBob, however. This episode is what many fans of the show consider to be her darkest role, and is what cemented her status as a villainess because she wanted SpongeBob out of her life so much, that she was willing to murder him in order for that to come into fruition.