It may be hard to forgive someone who has wronged you but in order to be free, you have to forgive.
Nothing you do to harm them is going to help you. When you hold onto the wrong that someone has done to you, you give them a form of control over your life.
(1) When you see them you replay the issue
(2) When you see them you get angry
(3) When you hear their name, you share the issue with another person
(4) They've moved on and are living a joyous life; you're still bitter and lonely.
Also, remember if we expect God to forgive us, we must forgive others. Matthew 6:14-15
Let IT/THEM go so you can live!