This achievement can be done in unison with the "Your Cousin Dances Naked..." achievement. Atongwe is the man you must track throughout the level listening to his various conversations. THE ACHIEVEMENT POPS AFTER ATONGWE ACCESSES THE TERMINAL SHORTLY AFTER THE LAST CONVERSATION!
DO NOT SHOOT HIS GUARD THAT SPLITS FROM HIM WHEN ATONGWE AND THE MAN WITH THE YELLOW HARD HAT GO THROUGH THE FINAL DOOR. The room is dark enough that the guard will not see you, just keep going as normal.
TIPS:
1) Only use Graves' suppressed rifle to kill people if needed.
2) Save often. Typically after every conversation Atongwe has (4 in total) and really at any moment you deem difficult or just for insurance.
3) Read this for tips on the conversation: