Many people who were hurt by an ex often ask, "How can I get revenge on my ex who used me, or who cheated on me, or who emotionally damaged me?"
Physically harming them, destroying their property, or maybe having sex with one of their friends is what often comes to mind. However, those things are either illegal or will not help you feel better over time.
The best revenge on someone who hurt you is simply living better without them. Yeah, I know, it's not what you wanna hear, but it is the best thing you can do. If you do things that are aimed at hurting your ex, you will basically be showing them that they really hurt you and continue to hurt you. You will be showing them that they still have power over you.
They will likely see any attempt as pathetic or humorous. And, of course, they will likely tell others about what you did or tried to do. Unfortunately, nothing you do will hurt them the way they hurt you.
I understand your pain and the desire to get back at them for hurting you. If the universe were fair, those who deliberately hurt others would be quickly served a dose of their own medicine. But, sadly, life's not fair. Nor will it ever be.
So, just live your life. Be the best person you can be. So that one day when your ex hears about you, they see that continuing life without them was the best thing that ever happened to you.