Is silence the best way to handle a desperate deluded ex boyfriend, or is it just best to write him a letter?

Me and my ex boyfriend had a huge argument two days ago. He is truly pathetic. I wouldn't sleep with him, and haven't been interested in him appart from as a friend for the past few years. Years ago i thought i was in love with him, until he broke up with me after i had a seizure, refused to be seen walking with me in public, and kept telling me to date someone my age and other guys. Alas fast forward, i have moved on and wonder what my attraction to him ever was? For ages he convinced me that he just liked me as a friend, so i didn't feel threatened about coming to see him. There was a time i was really vulnerable and it seemed like he was just being supportive. But he had another agenda, he'd ask me if i'd pop over and have sex with him, he'd make lewd comments about liking the taste of p*ssy more than lobster, he'd make comments like i definitely wanted to see him naked in the bath, or when i used to see him he'd harp on about missing our old scenario when i used to dance in front of his mirror naked. When i did do that, it was because we were seeing each other and everything about us even our conversations were highly sexual. For ages he seemed like just a friend, so i would talk with him about crushes i had, dates i went on with different guys, who i liked and why i liked them, and he'd tell me about dates he'd been on. In the end there was always something wrong or not quite right with these women, then he'd start trying to put the pressure on me to sleep with him. Saying that the problems i had with sex were a mark against me, guys wouldn't want me, they'd think i was too much, my beliefs about sex after commitment were ridiculous. He'd get really passionate, and aggressive about it, when at first he would pretend like it was just a debate he was bringing for discussion. If i so as missed his call, or didn't see him, suddenly he'd show up at my house, brooding, or trying to pick a fight with me. Recently i told him about some dates i was going on and he'd say things like 'dont get raped in a nasty tone," and i'm not dressed flighty, always in jeans or a tracksuit, i was excited about a guy and he said you know how it always ends, it's gonna end the same way and you'll end up running back to me. Once a few weeks back he just randomly showed up at my house in his car, told me to get in, we drov to his house and he was looking at me like i was a piece of meat. I made my excuses and disappeared. When he tells me about his dates, it's almost like he's trying to compete with me,it's pathetic. Usually he takes all these nasty digs at me, especially when i'm happy and progressing, or getting positive experiences with men. Recently he came to see me, i always go to see him. I was semi asleep, but i heard my brother was quite rude to him, as is the case with him, anytime he has conflict with a man especially if their from my culture he'll take it out on me. He called me on private number just to check if i was actually sleeping, he didn't say anything, just stayed silent on the phone.When i came round to chck on him, everything i'd told him in confidence he used against me. He said i deserved to be attacked even though he knew how much the attack had hurt me, even though he'd been attacked himself. He told his cat to attack and kill me, all because i don't have feelings for him, he even lied about the things that he'd done or sexual comments which made me feel uncomfortable. This is the same guy that knew i was about to leave his house, and would tell me he was going to die soon, and would i stay longer. He used to warn me about his ex girlfriend saying she was crazy, but i knew it was because she didn't want to be with him. Now he's calling me crazy, he's just such a looser, how do i ensure i never speak to him again?