You screwed up so bad that the consequences are the equivalent of getting fucked
Guy 1: Oh, I just teamkilled by accident!
Guy 2: OH YA DUN FUCK'D UP NOW!!
When someone has gone off & f*cked up on something.
Ex: Homework, a test, a relationship, realizing the regret of hooking up with your step-sis/step-bro.
It was at this very moment, Mikey knew, he dun fk'd up when he threw the mentors into the 3 Liter bottle of soda.