What makes him differ from Grumpy is that Scarface has a big scar going through where his right eye used to be, hence his name. It is believed that this makes his especially angry and vicious--far more so than mere Grumpy. He frequently chases the Porters, trying to make a meal out of them. Scarface has eaten the parents of Tasha. Because of his reputation of being a predator (he is a carnivorous T-Rex), Scarface is an enemy to everyone in the series, including the Sleestaks.
The only creature who is a match for Scarface in a fight is the Myzarnian Cyborg.