Enable win counter for multiplayer
On the title screen hold ZL and R. While still holding them, press Down, X, Y. If done correctly, a sound should play.
Maximum difficulty CPU players for VS mode
On the title scree hold L, then press Y before selecting a CPU player.
Permanently unlock all characters, skins, voice packs, and music
On the title screen hold L1 and R1. While still holding them, press Up, Down, Right, Left, X, B, Y, Y. If done correctly, a sound should play.
Will turn the player into a cpu
In solo or multiplayer arcade mode, On the screen where it says Play (after character selection). Hold down the R button or SR if using one joycon.