My previous post just reminded me of what is quite possibly my least favorite example of yandere ever. A spoiled, selfish yandere who didn't give a damn if the object of her obsession cared about her at all as long as he was physically there. She trapped him in his own mind and forced him to be with her, as well as mind controlling pretty much everyone else associated with the MC to go along with her in one way or another. There was no crazy eyes, nor any of the other stereotypical trappings of yandere like the manic personality or "I'm going to make you so happy, you'll see" that you typically see. It was almost anti-yandere yandere.
There was no cutting, violence, physical force, or anything like that. Just lies and mind control with a complete lack of anything resembling humanity. A perfect example of why the line for personal preference for yandere is so nebulous. On the surface it sounds great, in execution it just...wasn't.