Everyone's least favorite character in the whole series was Dolores Umbridge. I'm pretty sure that everyone wanted her dead more than Voldemort, and we can never forgive J.K. Rowling for not killing her off. I saw a meme once that said "If I was stuck in a room with Umbridge, Voldemort, and Bellatrix and a gun with two bullets, I would shoot Umbridge twice." And I had to agree.