How do I break up with him? I tried twice but he keeps hanging on?

I told him twice that it's not going to work out but then he keeps kissing me, even after that. I pull away and he still doesn't get the hint. What should I do?How do I break up with him? I tried twice but he keeps hanging on?
Tell him that you really just wants to be friends and that you now he still likes you and tell him he WAS a great boyfriend. Make sure you say WAS. And now you just want to be friends and break up with him. Say sorry we're done.