For me...
#1 Chi-chi - I can understand trying to slip in a pretty, yet slightly crazy female character, but as far as I'm concerned she's a poster girl for psycho *****es.
#2 Pan - As was already mentioned, what happened to that cute kid that almost went super because that brat from the junior division killed her ice cream cone? Pan honestly belonged in
this anime rather than GT.
#3 Maron - Pretty sure she's not canon and thank god for that. Complete dumbass. **** for brains. We already have a clueless character, Goku, who wasn't annoyingly clueless like this blue-haired bimbo.
#4 All Metamorese Fusion Dance characters(canon and non-canon) - Apparently a side effect of this dance is being an annoying, arrogant piece of overpowered crap.
#5 Oolong - A kidnapper with a thing for little girls... you sick ****.