Hint - How To Defeat General Raam Gears of War

In order to defeat Raam, you need to have grenades and a sniper rifle which is supplied in the center of the room before entering the boss arena.
after entering the arena, stay behind the wall you ended the cut scene with. This is important because you need to maintain your distance from Raam. Also, it helps to command Don to "cease fire." This will make him run back towards you keeping him alive longer to distract Raam.
The trick is to get Raam's swarm away from his body. In order to do this, you need to throw a grenade at Raam. If successful, the swarm will disperse giving you clear head shots using the sniper rifle. Repeat until he’s defeated.
If you run out of grenades or simply cannot aim them, just stay in the lighted areas of floor to avoid the Kryll swarm.
If you don't defeat Raam by the time he reaches your wall cover, move in the opposite direction he does and shoot when the swarm disperses. You will take damage from Raam’s machine gun, but you stay in the light which prevents the swarm from killing you.