27 Aug 2010 15 Oct 2010
This achievement is obtained by completing the "One Shot, One Kill" level, you can complete it on any difficulty to get the achievement so you don't have to pull your hair out over it on Veteran, however if you are playing on Vet chances are there's one particular part of the level you'll find more frustrating then the rest of the game combined, it's the last portion of the level where you have to wait out evac in a small abandoned playground, I'll link in the video guide to the level so that you can see how someone did complete it,
Just keep at it, this game has a low TA ratio but at points can be incredibly frustrating, it's not impossible, so many people have managed to beat it and so can you!
Note; I realise this achievement doesn't require a Veteran solution but I decided it best to cover the hardest approach!
*Credit to zyon1989 for the videos.