Anyone out there willing to try and take this down with me? The achievement is awarded for completing Ch.3 of Episode 2 with at least one marine left alive. It's actually a lot harder than it sounds and near impossible to do solo. I was almost able to reach the final part with the phantoms with one marine left but he died shortly before. I imagine it shouldn't be a problem with a co-op partner, especially if there's 3 or 4 of us.
If anyone is interested I'm looking for now / the next hour or so. If not I'll be online tomorrow evening. Just send me a message on XBL.