Here are some tips for beating the final boss.

For the first part
Use Empower to get through his shield. Use explosives -- the Panzer Rocket Launcher and the Veil Blue Rocket Launcher.

For the second part
You can use either the Slow Motion or Empower once again to beat him.

For the third part
Don't run up the ramp. Snipe him with a Sniper Rifle or Rocket Launcher. Go slowly. Once you get to the part where you need to climb up stairs, get a weapon ready to kill large amounts of those things on 4 legs (they call 'em Sniffers). There are 4 waves of them. Afterward, simply shoot him until he falls.

For the fourth part
Simply shoot him since at this point he will have no power ups. Use the explosives to end him quickly.