In Proton: Age of Empires 2 DE multiplayer went out of sync which ends the game. BeamNG Drive (now Linux native but wasn't a year ago) took 20min to preprocess shaders, then was laggy compared to Windows on the same machine, then reproducibly crashed from a memleak. Both were known issues on ProtonDB, but the rating still said "gold," so I stopped trusting the ratings.

Dolphin is Linux native. Works fine except for the huge input lag using GameCube controllers (via wii u adapter which is the only solid way), which means I can't really use it. Known issue with some driver, I tried a kmod to overclock it but no dice.