The Chronicles of Riddick: Assault on Dark Athena

In order to get the mech you must first kill the pilot. Luckily there is alot of darkness. Unfortunately, he has very big guns. First take cover behind the line of crates and crouch. Using "LB" hold up so you can shoot over the cover. Fire a few shots and duck down until he stops firing. When he gets close and tries to flank, move round to the other side of the room, staying in crouch so you can't be seen. Lure him over with a single shot and then go back to your crates. He should be looking the opposite way so grab your shotgun and fire at his back until he goes down.