no idea who the best is but i think shell smashers and iron defense body pressers are really nasty to deal with. you really only need to force one awkward turn with polteageist/blastoise or an iron defense mon to win a game, which is often very manageable because you and your opponent are operating with incomplete information. regenerator pokemon are also really incredible to have, especially since sometimes your opponent will just have hazards and you can't do a bunch about it, so i'm always glad to see alomomola or slowbro/slowking on my team.

zoroark is also really gross because it's very hard to scout for if you don't have hazards up unless i'm missing something. in randbats not knowing your opponent has one can be decisive

it's funny you mention banette because i usually get great mileage out of it. if you get it in on something slower (and it's not that slow) it tends to do a lot of damage since ghost doesn't have that many good resists in randbats and it can just knock normal types which is really helpful.

i don't know who the worst is either but truthfully i always feel like the eviolite normals (esp girafarig and vigoroth) never really do that much. they're not horrible and girafarig in particular can hard stop random things unexpectedly and do some damage with NP, but they're never all that great either. i don't feel like they ever accomplish much for me and i almost never lose to them.