Seeing this competitive: Confusion. I think Paralysis is next to that. And infatuation on some level. Or rather, let's just do it like this:
Confusion and Infatuation are on the same level of annoyance here. With Infatuation, your pokemon, chances are, isn't going to move and you're going to be really lucky if they strike a hit, whilst your opponent is just going to sit there, setting up on you in like 50 different ways and its gg from there. @_@; it's the same thing with confusion, except there's a huge risk that you might kill yourself, thus giving your opponent a free turn. Meh.
Though speaking of these things as far as in-game goes, I still find infatuation to be a pain to put up with, but Paralysis becomes increasingly annoying and and a pain to tolerate.