Most Helpful Guy
The best way to try to hurt him is for him to see you happier without him than you ever were with him. Whether you are alone, or with someone else, show him you are doing just fine without him, and make him curious about if his life could have been better had he stuck with you.
Whatever you do, don't go "psycho-ex" on him, no matter how bad he hurt you. Leave his new girl alone (if he has one), leave his property alone, do not stalk him, threaten him, etc. Not only is there a potential of legal trouble, all "psycho-ex" mode does is reaffirm to him leaving you was the best possible choice he could ever have made in his life.
The more time you waste seeking "revenge" for his transgressions against you, the less time you leave yourself being happy.1