Instructions
Grab the weapons and the ammunition found in the train car before you face RAAM on the final platform. If you wait a few minutes after getting the goods, the supplies will respawn so you can use this tactic to ensure you have maxed out all of your ammo for the tough battle ahead.
Use your Longshot sniper rifle to hit RAAM with a quick shot before he sends the Kryll -- bat-like creatures -- at you.
Hide behind a crate that's bathed in light from one of the spotlights to avoid the Kryll and RAAM's bullets. If you're in the shadows when the Kryll flies your way, these nocturnal creatures will kill you.
Toss a grenade at RAAM when he begins to walk toward you to slow him down and damage him.
Run across the platform to the opposite side when RAAM gets closer to you.
Repeat Steps 2 to 5. After a few sequences, RAAM should fall and the achievement will unlock.