Oh... I realized... my personal most hated character is the Kai Winn. I'm mid-way through Season 3. Don't know if she changes later on, but right now I cannot stand her. I know she is meant to be disliked, but either way I seriously do not like her at all... so unworthy of the position.
I haven't peeked much at upcoming episodes, so forgive me if she changes later on in the show.