I use to be able to use Olimar... good times. I tried to use him recently and failed terribly -.-.
Anyway, the character I hate the most is (drum roll please)... Ike. I've always had about 0 friends on at any given time so I was prone to do random matches... and Ike is annoying. About 95% of the people (or more) who use Ike on random are just... hmmm... can't think of one word that sums it all up, so I'll do three: noobs, spammers, and campers.