I don't want to reconcile with an old friend
Can you tell me why you don't want to make up with your friend?
I do not want to forget about the past when they hurt me, it is really important for me not to dismiss their mistreatment of me.
Not reconciling with your old friend is understandable if they hurt you. However, holding on to your resentment is unhealthy. It will help to let it go and move on.
I'm not usually an angry person, but I want them to know how much I hate them.
I don't think holding on to that anger and hatred for your friend is a good thing. It would be better if you talked to them about it or let it go and moved on. Both of you would be happier.