a fucking knobhead
Someone so tremendously fucking stupid, they could be classified as Sub-Doorknob in intelligence. Specially used when someone still cannot use "Their", "They're and "There".
P1: Hey, I think that's they're wallet, you should give it back
P2: In the least amount of respect possible, you're a fucking knobhead.
P2: In the least amount of respect possible, you're a fucking knobhead.