Hi guys! Me and my big cuz struggled on the 9th Halo Reach level.
I found a way to do this with only 5 tries.
You need to kill the grunt on the ghost at the small waterhole and take his weapon. Fire at the shade turrets and ghosts. The other player has to use the DMR to snipe on the guys with the massive green laser thingys. Get past the ghosts and revenents to get to the last one. You must kill most enemies first. The last Revenent will be hard, take it out by hiding behind a pile of rocks and sniping at the guy at the top from the side. The other player will distract it, every time they die they respawn near you. This should help you complete the level. Thanks and Merry Xmas to you all!

Oneman-Onegun