I'm thinking of ghosting my suicidal friend
Why do you want to ghost your friend?
I know a little bit about him. He is a self destructive personality. He is also manipulative and cuts himself often.
I understand your frustration when it comes to dealing with manipulative people. Regardless, he is still your friend and you should get him help not leaving him. Call 911 if he threatens to kill himself again.
Nah, I'm not just going to sit by and let him kill himself.
When a friend is in trouble and threatening to kill themselves it is a message to you that they are asking for help. Not helping them by sitting by is not being a friend at all. Get your friend the help he needs and support him through his long road to recovery.