The achievement for Those Left Behind, which is to have at least 1 Marine alive after completing the Tayari Plaza mission, isn’t unlocking.
Took me a few times. I finally started checking the map and verified that it had a friendly IFF tag on the map before proceeding to the final area with Dare’s pod. The only one that showed on my map was the two from the very beginning, the Marines that are in that last major area don’t seem to count. This was rather difficult even on easy.