As we were saying, Dolores Umbridge is infuriating
.
I really, really hated Baldur Persicke from Alone In Berlin; he's a teenage Nazi who's very sly and is very cutthroat to get what he wants, and generally represents the SS and Nazi Party; and in the context of the book is the only person with a happy ending, despite being a Nazi (the storyline takes place during the height of WWII).
Mr. ___ in The Color Purple riles me up as well. He represents oppression of women.
Generally just characters who oppress and get away with their crimes or flaws in the face of the good characters not prevailing. -is sad-