I'm going to end my friendship with a friend of almost 8 years and promise myself to never help him again
Why do you want to end the friendship?
He talked shit about me to other people
Friends should try to work things out but sometimes it is impossible if they do bad things to you. Then ending a friendship is the right thing to do so that you can make friends with better people.
I don't want to talk to him ever again.
It can be hard to end a friendship but you should if the friendship is not working out for you. You feel betrayed by him and it is okay to be upset and not want to be friends anymore.