Mienshao, Klefki, Bergmite, Voltorb, and the entire Alolan Meowth line.
I have nothing but seething hatred for Mienshao. Of course it just had to pull a boosted crit on a teammate I treasured greatly, and forcing me to cheat. I just loathe it, and I never want to use it.
Klefki is just... yeah. I've tried using one and it wasn't good at all. No particularly good stats, no interesting moves, nothing. I also just can't stand it's design too. It isn't cute, it has an ugly face, and really, a beard? That weird drop on it's chin, it looks so out of place and kills the whole design.
Bergmite for the same reasons as the above, pointless, extremely weak, shouldn't exist at all. Would never use it unless I was desperate.
Voltorb for no reason, it just is.
The Alolan Meowth line is the worst out of all of them. For Alolan Meowth itself, it's just Meowth recoloured and has a stupid smug face. The worst part is that I get it way too much on wondertrade, and it's smug face is like it's trying to troll me or something. Alolan Persian is by far the worst creature to ever enter the pokeverse. I cannot take it seriously at all. Whether it's because of it's expression, the really big head, the fact it is still just simply another bland recolour makes it the worst design in the games bar none. Even thinking about Alolan Persian makes me angry. I already was expecting it to not be that great, but I didn't expect it to swoop down this low, and be simply horrendous.
I might use any of the other 4 I've mentioned if I had no other option, but I will NEVER use Alolan Persian ever, as long as I live. I will always ban it from every playthrough I make.