Vicki
God, he's done so much it's hard to keep track of everything. He used Elena and her blood to turn a bunch of people into vampire/werewolf hybrids, including Tyler. Which I know, he was a total asshole to you, and the whole thing with Mom, but...he almost killed Caroline a couple of times, he's kidnapped pretty much all of us at one point or another to convince someone to do something for him. He killed Tyler's mom, drown her in the town fountain.