Behemoth

Behemoth, or other wise known as the unconquerable beast of the land, usually seen in forests and vast places.

Overview
Behemoth is a boss type Hellion that uses two different physical attacks. It is immune or highly resistant to all means of slowing its physical damage output, including 80% resistance to power break. It has no elemental weaknesses, but has next to no magic defense or defense, making an overkill easier.