Most Helpful Guy
Find a guy who is better looking, nicer, doesn't cheat on you, and makes you happy. Don't do it because you want to make him jealous, do it to treat yourself better. The less your ex's infidelity bothers you, the better things will be for you, and the more it will piss him off.
Most Helpful Girl
By breaking up with him and acting mature by not stooping to his level. Don't even look at him afterwards and ignore his begs to get back together.