Fellow DM’s what ridiculous homebrew have you rejected?

I’ve only ever DM for one ongoing game and my players homebrew items or feats are usually pretty balanced and if not it’s just a matter of tweaking the numbers. Only one homebrew feat was so ridiculous that I told the player “at the end of this session pick another feat or stat increase, that homebrew feat is banned” it was a feat that gave bonus effects for upcasting and ended up with the player one rounding a dracolich. What super op homebrew have you rejected or banned after it was used?