At one point Donald got on my nerves because I couldn't understand what he was saying half the time and he has a crappy personality, but Donald is an unoriginal answer, I gotta think about it more...
Frollo. The guy is such a douchebag and completely unlikeable. A character that I amor to hate. Sarousch was a hell of a lot más likeable and was funny too.
If disney Channel, disney XD, o disney Junior characters count, then, I say conservar en vinagre, salmuera and maní, cacahuete from the disney XD show, "Pickle and Peanut" are the most annoying characters disney has ever created, if Walt disney was still alive, I think he would be horrified if he saw this show.