Hell Pig

Archaeotherium
National Museum of Natural History, Smithsonian Institution, Washington DC

This is a type of entelodont, a distant relative of modern pigs. It's odd teeth, though similar to pigs, indicate scavenging on meat playing a larger part of the diet. Though one might not think a pig is the scariest thing in the world, this animal could have looked you in the eye, with a shoulder height of about two meters. They were the apex predators of around the Oligocene-Miocene boundary across the northern hemisphere.