easy, if your actually good and you beat the game a few times on insane, run up to him with a shotty, shoot him and run away. He doesn't melee like other Locust, only shoots. Also, if you wanna try, there's a machine gun near the resonator up for grabs if you wanna use it to shoot RAAM. The easiest way to kill him is just use a sniper, pistol, and shotty. If you need help, send me a message and i can help ya with it.