Dolores Umbridge from Harry Potter and the Order of the Phoenix. She added to the plot, yes, but she's an insane b***h... Especially with the bewitched pen. That seriously made me say, "What the ******** was she thinking when she wrote out Dolores' character?"
Sandy and Dennys Murry from the Time quintet. Honestly, I hate them... I hate the way they treat the rest of their family. How they can act normal is just beyond me. That's the main thing about them that pisses me off - they're normal.
Andrew in The Chronicles of Narnia: The Magician's Nephew. The way he used Diggory and Polly really irked me, and he even attempted to cheat on his wife with the White Witch gonk
The artist in The Oval Portrait... Yes, it's a short story, but he's a b*****d. Not checking on his wife, endulging himself in his art for days on end. His name was never mentioned, but I hate him scream