The "crazy/terrible girlfriend" trope appears everywhere, including anime; while certainly an overused, and many times sexist, descriptor, such a characterization does feel appropriate when describing the worst anime girlfriends of all time. Given the number of dysfunctional anime relationships out there, it stands to reason a few terrible anime girlfriends are a part of them. While everyone follows different criteria for what they want from a partner, most agree that a few things are of critical importance when it comes to showing basic respect for your partner as a human being. Not manipulating them into doing things they don't want to do. Not cheating on them. Not stalking or assaulting them. Not murdering them.
This an an extremely low bar, but sadly, there are plenty of anime girlfriends who can't manage even that much. Some are murderous stalkers like Yuno Gasai, and others are prone to physical violence like Naru Narusegawa. No matter how cute they appear, you definitely would not want any of these ladies as your girlfriend or your wife. That said, don't think that anime only makes the ladies look bad: plenty of boring anime men out there make for equally terrible boyfriends, and honestly, they're probably the reason why all these anime girlfriends are acting out.