I'm going to block my ex-fwb current friend without telling him
Do you have a reason for ghosting him?
I want to punish him for making me feel guilty after he made me feel guilty.
Nothing says that you need to be friends with an ex-partner. If they are making you feel guilty over something you should think about just stopping communication with them.
It's worse. I could have sex with him back then and now I have a BF. I'm going to ruin his life, it will teach him not to cheat on his gf and make her feel guilty.
It is normal for people to move on after they end a relationship. You should not make drama because you could cause your new bf to be turned off by what you do.