I hate all of them, but especially Paralysis, Sleep and Infatuation.
Paralysis makes me dread battles with Pokemon that have Static cos I hate getting my Speed cut and having that chance of not being able to attack (forget about the Speed drop if you have a Pokemon with Quick Feet).
Sleep is my most hated cos I hate being unable to attack while the opponent just pummels me. That's why I often try to use healing items or run back to a healing spot. Especially with all those Audino using Secret Power, which can put any Pokemon that I'm training to sleep and man it makes me mad cos it almost ALWAYS HAPPENS!
Infatuation, especially in B/W due to most wild Audino carrying Attract, meaning that if I'm training something of the opposite gender I have to be careful cos when Attract hits, I get stunned into only attacking 50% of the time and I always often fall to it. It also forces me to switch to a Pokemon that is of the same gender or with the Oblivious ability just to prevent it. Audino made me hate infatuation even more!