Poison-types in general. Specifically, there's Weezing, Arbok, Victreebel, Trubbish, Garbodor, and Qwilfish. As far as non-Poison-types go, there's Dunsparce, Basculin, Carnivine, and the Klink and Tepig lines, just off the top of my head. Trubbish in particular, I believe it to be the cutest Pokémon ever to exist, and Garbodor is one of the most awesome. And Weezing is my favorite Pokémon, period.
I actually don't dislike any Pokémon, really. Well, any species of Pokémon- there is one Pokémon I hate, but it's a specific specimen I dislike, as opposed to the species as a whole; the Miltank of Death. I think we all know which Miltank I'm talking about here.