The model should be a gigantic human warrior, with a sword and a shield. His primary attribute is Strength, and he is a melee range hero.
Skillset: Sever Artery:
Swing at the enemy and cut deeply into their flesh. For the next 8 seconds they bleed out, inflicting 10/20/30/40 damage per second, and giving the debuff Bleeding, which slows enemies for the duration 5/10/15/20%.
Strike the enemy for 100/150/200/250 damage, and if they are bleeding, inflict 20% of their maximum health as damage. This health is regained in 8 seconds if the enemy doesn't die.
Big Rig is able to recognize his enemy is near death, and as such he deals an incredible amount of damage but leaves himself open for attack. Deals 100/200/300/400 damage to the target, and if they're under 50% health, deal an additional 50/100/150/200 damage. If Big Rig does not kill his opponent, he becomes exhausted, slowing his attack and movespeed by 50% for 5 seconds and losing all of his remaining energy.
Big Rig Charge!:
All allies are inspired by Big Rig's courage, making them move 10/15/20% faster for 6/8/10 seconds. This effect is global and has no cast time.