I'm looking for any games where one of the characters is obsessed with the MC and I don't mean a normal obsession, like an unhealthy obsession people would be worried about irl.
The trope you're looking for is yandere.
In Love & Sex Second Base one of the characters stalks you and you have to manage her obsession.
Degrees of Lewdity has one as well (You can pick their gender, like you can with all the NPCs).
It's on Steam and has a patch: Obsessed Lucy. It's in the title: the game is all about your obsessed sister. It does have AI graphics but they're really well done IMO