River. I found her so annoying. I didnt like her in the show, I didn't like her in the movie, I dont like her now!
I hated that she was the center of anything and I hated that she was the center of the movie. Well I don't hate, I mean I don't take it that seriously, but I did find her story more of a nuisance than something interesting.
I don't like the actress either so I'm not sure if I didn't like the character of I just didnt like how the character was being portrayed. Everyone I have introduced Firefly to have been severly annoyed by her character so at least I know I'm not alone!