Haha, this is risky... I usually try not to talk about characters I dislike, since I want this to be a mallerollo + other characters I like blog and not one where I gripe about stuff I don't like. But...
Due to personal circumstances regarding my upbringing, my least favorite character is Kalim. I don't think that he's bad as a character. If anything, eliciting such a strong response from me means something went right. But he just rubs me the wrong way, I really can't stand when he doesn't listen to people, how he dumps parties on Jamil with little warning, etc. I don't hate him. I'd like to see him develop more over the story, but thusfar he hasn't changed as much as I'd like.