Scorpion

Scorpion is a bounty hunter who lives in the Badland in Alabasta after retiring there to raise his two sons, Chip and Dip, and a passionate man who dedicated himself to try and capture Ace.

Scorpion is a middle aged man, with brown hair and a beard. He has a black helmet with a red scorpion mark and an arrowed-heart tattoo on his forehead. He wears a squared red shirt, black long-sleeved undershirt, knee-length overalls with pants underneath, and brown shoes.

The Prescorraci Rifle is Scorpion's personal weapon. It is a backpack weapon that can shoot acid from its target hose. Ace manages to escape the acid shot at him, but it is shown to be powerful enough to break through rock. He can also shoot a very strong bomb, that, upon contact with a surface, will protrude spikes from its shell to stick to the surface before detonating. He also has a steel net that can be shot out of his bazooka.

(Source: One Piece Wikia)