Most Helpful Guy
I don't think, in this case, that you need to tell him that you have forgiven him, because if he is as narcissistic as you say, it wouldn't mean that much to him. Forgive him in your heart as it is about you letting go of the hurt to enable you to move on with your life and leave all of that behind...
Most Helpful Girl
It's a good think you didn't say anything. It's good that you forgave him (to yourself) because it's not good to hold on to that hate, but he doesn't need to know that.