Originally Posted by Opiate42
Thanks for the clarification, some buds and I did this last night several different ways and it never unlocked. One friend did it solo Legendary, saved both terminals and it still didn't pop. When we all teamed up, we tried on Normal and on Heroic, one dude survived with no deaths, but still nothing.
I think there may have been an enemy hiding somewhere we missed before hitting the orange button.
Try playing it co-op with 4 randoms. Seems this is the way people are able to get it - making sure one objective survives, and all enemies are killed.