How to tell your ex to leave you alone nicely?

My ex keeps contacting me saying he loves me. I've told him before that I stopped loving him long after we broke up. I told him I loved him like a brother. I didn't cheat on him because we weren't official so I moved on to another guy. He finds out and says I cheated on him, but how can I cheat on him if our relationship was always a secret? We were fwbs and then I thought I was in love and we became sort of boyfriend/girlfriend until he said I cheated on him and called me every name in the book, which lead me to get over him quickly. We broke up like 2 years ago and dude is still irking me. He keeps saying we're going to get married and he proposed to me. I never gave him an answer but I told him I didn't want to get married. How the hell do I get rid of him?
How to tell your ex to leave you alone nicely?
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