There aren't really bad abilities per se. Granted, some abilities, like truant (you can attack only every other turn) and slow start (have speed halved for the first five turns) are there to try and balance out a powerful pokemon. But in the right hands, you can even use abilities like these to your advantage. Klutz is great if you have an item like toxic orb, and you want to use it on your opponent. With Klutz you don't have to worry about it hurting you before hitting them with it.
