Twenty years is a very long time to carry this burden. You may have left the practice 20 years ago, but you are still carrying that bully around in your head! He doesn’t deserve that amount of power. You don’t deserve to suffer like this.
One thing you could try with your counselor is this: Write a letter to the bully. Write everything you want to say to him. Don’t leave a thing out. Then try the “empty chair” technique. Sit across from an empty chair and imagine him sitting there and that he has to listen to you. Then read your letter to him out loud. Tell him how you’ve felt and how angry and sad you are. Get it off your chest and out of your head.
I do suggest you do this with a counselor. You may find that this will evoke some strong feelings. A counselor will help you safely sit with the feelings and then learn from the experience.
Many people find this kind of role playing as a way to get something out in the open so they can deal with it more effectively. I hope you find it helpful.
I wish you well.