Bellatrix because despite the fact that she’s an awesome character and I love her, she has a racist rhetoric which is worse than Umbridge’s. Her morals are all over the place and she’s the most unstable and destructive

It was between Peter pettigrew and ulbridge and I picked Peter pettigrew

Greyback is an allegory for an adult who sexual assaults children, so he is pretty much the worst. He is also a cannibal.