Sorry Vizier, Im jumping on your coat tails here as you created the thread about what fictional characters people like, I thought id make one about the characters people despise.
Bella Swan (Twilight) - seriously, Bella infuriates me to no end. I disliked her in the books and furthermore on the screen as well. She's so indecisive and i find that bothers me a lot. Sorry to hate on her Twilight fans.
Dolores Umbridge (Harry Potter) - wow that woman knew how to make my blood boil. Nasty woman!
Johnny Storm (Fantastic 4) - I found him to be immature and downright annoying in the movie.
Sam Witwicky (Transformers) - I liked the cartoon version of him, did not like the way he was played in the movie by Shia Labeouf.