Lady Macbeth- Lady Macbeth
Although Macbeth was the one who held the sword, it was Lady Macbeth that manipulated him into taking the lives of many. In fact, one of the most recognizable scenes in Macbeth is when she hallucinates blood on her hands from Macbeth's many murders caused by her mention. Although she gets her share at the end of the book/film, that doesn't change her effect on history, and it doesn't cleanse her of her sins.
Miss Trunchbull- Matilda
If you haven't seen Matilda, you should drop what you're doing and watch it right now. Miss Trunchbull is a purely evil character that abuses and humiliates children. She force-feeds a child an entire chocolate cake, swings little girls around by their pony tails, and all because she envies the children that come to her because of their youth, how sad.