In phase one, use Empower to get through his shield then first the Panzer Rocket Launcher and the Veil Blue Rocket Launcher. In phase two, use the Slow Motion or Empower to defeat him. In phase three, instead of running up the ramp, shoot him with a sniper rifle or rocket launcher. Move slowly, and get to the stairs. Have a weapon ready to kill the four waves of Sniffers. Then, shoot him until he falls. In phase four, just shoot him and use the explosives.