How do i unfriend someone?

There is this other boy that everyone doesn’t like. It’s not because he is a bully, it’s more because he just comes off as distracting, disruptive, and annoying. Nobody likes him and I’m one of his only “Friends”. He thinks I’m his friend only because I’m the only one that’s nice to him. But the thing is, I never really wanted to become friends, he more of just declared it himself and I went with it. I often feel like he is dragging me down and there are other people I would like to spend my time with. I can manage to deal with him during school hours, but I just don’t have the energy to deal with him once I get home. He also told me one day while I was playing a game, in the chat he said,”You’re being mean and rude! I’m going to text Your mother about this!” And he did. She brushed it off obviously. Like bruh, literally all I did was say,”I don’t feel like calling you right now, but I am open to communicating in the chat.” Calls me rude and saying that I’m a horrible friend for saying no thank you? HELP