Why would your ex downgrade from you after a relationship? I find myself attractive and he isn’t very. But the girl he is with now has nothing going for her. He wasn’t good to me when we were together and he treated me like shit, but with her he is so much nicer and really likes her. I don’t know what I did wrong, help?
LemonVibe 
Maybe you were too high maintenance or maybe he’s a narcissistic jerk face. We will never know from six sentences. What does it matter now? He’s a ex for a reason. The best way to get back at any ex is to move on and be happy with your life.