I think I have to stop being friends with someone I know.
Oh, no! Why do you want to stop being friends?
My friend is so boring and what he says is meaningless for me
Even if you've been friends with someone for a long time, people can grow apart or no longer put equal effort and care into the relationship.  Talking to them and communicating with them gives you both a chance to break it off without regrets.
I just want to hurt them and I don't care.
I think it's a bad idea to hurt them on purpose. I think you'll have fewer regrets later if you talk it out with your friend first.