Trust me this is worth reading I beat insane the first day. Dont get off the turret, once the reavers come around the mountain start shooting, when they get behind you leave the turret and open up with your hand gun( lancer is fine but handgun has accuracy ). Finally, when the reaver is next to you concentrate all your fire on its head, not the gunner!, if you shoot the gunner you wont have enough time. Sustain constant fire on the reavers head and hold RB as you shoot this way you dont switch buttons it just cools when your done fireing. There is another way though, my 11 year old sister did this and i have know idea how but she saved a frag from the first mission and tagged the thing by throwing it, dude!!!! Anyway, im 14 and im looking to be a progamer so if your on live id love to team up, gametag is THOR,:thumbup: Goodluck.