There's plenty of Pokemon throughout the regions that I hate, but I really just wish there were no Pseudolegendaries. I don't personally hate their designs, it's just the idea that there's Pokemon with stats competing with Legendaries isn't fun to me.. It makes so many unique Pokemon useless in comparison.
I've hated Lucario above all else because of it's fanbase though, it's just overrated. No more efficient on a team than plenty of other Pokemon.