For me it's making a character too obvious. Like stereotypes are fun to play with, but I don't wanna make a character be just their stereotype, even when they lean hard into a trope.

Evil looking mad scientist? Make him a pacifist.

Yeehaw cowboy who carries 2 guns with him everywhere? He's an environmentalist protecting endangered pokemon.

Punk rock musician? She's a pretty cheery, kind and polite person.

The honorable tribal warrior? Well he's only like that at his gym and a ball of anger everywhere else.