I want to stab my very close friend
That could get you in jail! Why do you want to stab a close friend?
He spent so much time on his so-called boyfriend over me.
Being in a friendship involves caring for another person. Stabbing a friend is a betrayal of their trust and feelings for you. If you're upset with them for not spending time with them, then have a discussion and be honest with your feelings.
Oh he is a bitch and deserves it.
But he is your friend, how does he deserve getting hurt when he's just finally found a romantic partner? I think you should calm down a bit and take some time off to yourself. If you had a new boyfriend, wouldn't you want to spend a lot of time with him too?