City, Spurs and Villa are the worst for me.
I never liked City much anyway but ever since Sheikh Mansour arrived they've been atop my most hated list, purely because of their fans, and Balotelli. He's such a pleb. Spurs just bug me. Villa, especially under O'Neill, played the worst, most boringly depressing football ever, then just seemed to pop up and score at proper random moments. Usually at the end of games.
Never keen on Arsenal either, but that's usually because we seem to be their favourite whipping boys on the rare occasion they fancy playing properly.