I don't know if I actively hate any Pokemon or character, but I do get tired of seeing the same Pokemon all over just because it looks cool or has been marketed as popular. Zorua and Zoroark are the ones that annoy me the most, I think. Also Victini. I don't understand what is so great about Victini, honestly.
And any fans that could be classified as "rabid" irk me, regardless of who they're a fan of (though Riley and other "pretty boys" come to mind).