Minimise Alolan Muk in the Battle Tree. Who designed this garbage? It's the absolute worst thing to face in the tree and I can't do anything to stop it with my current team as my Taunter has Prankster and my Z-Move is Ghost type. I hate this thing so much. It's gotten so bad and so common (I don't think I've ever faced Colress where he didn't bring this thing and it's usually a 50/50 chance that he appears for me) that I've designed a team for the sole purpose of countering it and other evasion reliant Pokémon. Good luck ruining me now, Muk!
Then there's Walrein. 2 of them in fact. Set no1 - Stockpile, Rest, Frost Breath and something else (Snore IIRC), and set no4 - Rest, Sleep Talk, Sheer Cold and Fissure (with a Lax Incense to boot)! These are always annoying because no1 takes so many hits to go down and no4 is just downright cheap. Is it wrong that I'm actually going to throw no4 right back in their face? Probably, but I don't care.
I've also been seriously lacking in Scald burns and Poison Point activation while the opponent seems to get flinches, crits, parahax, burns and everything else a lot more than they should. That is infuriating.