Is it normal to miss someone who treated me badly?

Psychologists call it intermittent reinforcement. When kindness arrives unpredictably, your brain values it far more than kindness that's reliable, because it never knows when the next piece is coming. So the good moments with someone who hurt you can feel more powerful than a whole year with someone gentle. Missing them doesn't mean they were good for you. It means your brain was trained by the pattern, and missing them and being glad they've gone can both be true.