I feel like I want to block someone over a roleplay.
How did it lead to this? Why would you want to block him?
He double-crossed me so I want the guy dead.
Blocking someone you don't wish to talk with is fine, but you should not wish someone to die. Wishing death on someone is never a good thing to do. If someone finds out you think like that, they will probably not want to be friends with you anymore and they will view you as a very bad person.
I want to hurt the guy.
It seems a bit extreme to wish him the level of harm you want to deal him. I know you as such a forgiving person too. I bet he really pissed you off, so I can almost feel your level of frustration and I hope you give it a few more days to let this anger dissipate because I care a lot about you and your emotional state.