Curses at customers if they get your order wrong.
My mother ordered a beef with broccoli lunch special with fried rice.
The guy gave her beef fried rice.
My mother told him the order was wrong, to which the guy blatantly said, "You f*cked up your order. Too bad."
Unbelievably rude. No matter how good the food is, no one should be talking to a 70 year old woman with that tongue.