29 Aug 2008 14 Jul 2009
This is arguably the hardest achievement in the game as it is known to be glitched for some. I thought it was too for me but refused to believe it, and I am pretty sure I discovered the problem.
There are approximately 10 guys in the tunnel when you are in the car that you must pop with the shotgun. Make sure you go into settings and turn your senstivity all the way up and autoaim on full. The achievement description says you have to kill all the workers in the tunnel. However, many have reported it after getting it on their 5th or 6th and others.
The way this achievement works: When you kill one worker once, the achievement registers that you killed that worker. So if you kill worker # 1 on the first runthrough, you technically don't need to worry about him on your next run through.
There are a few that are tricky to hit, once you get he hang of their positions, and finally hit them as well the achievement should unlock.
You will get frustrated very quickly, as you will have to watch the opening cutscene repeatedly. Take your time and you will eventually get it. It is not unattainable for anyone. It just unlocks in a very strange manner. Good Luck