So can we talk about
Ultra Necrozma because holy shit that thing is monstrous.
Like, that's the kind of thing you'd expect to deal with as some kind of uber difficult bonus boss. Not an actual thing you have to face in the main story.
I was using a larvesta because well masochist run, of course i'm going to use the Pokemon that evolves only once at level 59 and it evolved right before that battle so I was expecting to just steamroll through the rest of the game with Volcarona but
Ultra Necrozma took it out with power gem and it just wiped the floor with everything else in my party. I equipped a focus sash on Volcarona so I could get a hit in but it managed to survive a STAB*, Super Effective, 75 Base Power, Critical Hit! Signal Beam coming off of a 196 Special Attack. Granted it had such little health left that I was able to finish it off with Lopunny's fake out (which is guaranteed to go first and makes the opponent flinch so it's basically a free hit although it doesn't do much damage.) but still.