I'm going to abruptly end this friendship
Why do you want to end the friendship?
He is not a good friend. He has insulted me several times.
Friends should work things out but it is understandable that sometimes you can't. If a person hurts you it is better to end the relationship, rather than to keep suffering.
I thought he was just misunderstood and I wanted to help him.
You tried your best and there is nothing wrong with that. If the friendship isn't worth it, you should move on.