Spoilers) Charm setup to cheese Failed Champion. For this to work hold super dash at the top of one of the arena walls, and make sure to attack home when's he's down
Hollow Knight: The False Knight Boss Guide
A tier list based on how cheesable each boss is. : r/HollowKnight
How To Beat Failed Champion Easily - YouTube
Hollow-Knight-Bosses-Ranked-Failed-Champion - The Punished Backlog
Found a way to cheese the Failed Champion, is this widely known? : r/ HollowKnight
How to cheese the failed champion : r/HollowKnight
Failed champion fast cheese (using old nail to prove a point) : r/ HollowKnight