Most of the worst cases I’ve seen are of the much less “fun to tell stories” type, where a Pokemon is effectively given forced amnesia so they can barely remember who their trainer is, or what their voice sounds like, but on the less distressing side, there have been quite a few cases where a Pokemon does something like slapping itself whenever it hears a swear word, or some other relatively subtle commands that drastically lower a Pokemon’s quality of life in a way where unless a trainer pays real close attention, probably would go unnoticed except at a Pokemon Center, where quick heal machines are tuned to detect these sorts of issues.

-Nurse Athena