When someone hurts your feelings, the immediate response is often to lash out in anger. This is especially true when you have romantic feelings for a guy. When you feel cheated or used, the pain can be unbearable, but try not to react right away. You may eventually regret any irrational decisions, so prepare yourself ahead of time. You want to clearly communicate your strong feelings without doing or saying something foolish.
Write down your feelings on paper. Express why you hate the guy by writing down actions he did to hurt your feelings.
Prioritize your thoughts to the actions that hurt you the most. Prepare the list of the points you want to tell him. Change the statements that blame, or the "you" statements, to feeling statements, or "I" statements. Instead of saying, "You cheated on me," say, "My trust and love were compromised when I heard you were with another woman." These types of statements keep him from getting defensive.
Call him on the phone or set up a time to meet in person. Speak in a calm and cool voice without yelling. Have your list in front of you so you don't stray off topic. You also want to make sure you express all the reasons you hate him.
End all communication. Delete him from all social media accounts and delete his phone number. There is no reason to continue communicating. After you have said your piece, move on to healthier relationships and leave the past in the past.