Its better to track this achievement with the one for Mein Leben known as "Ultimate Spy." Fun Fact, you only need to beat the last Volume in order to unlock the difficulty based achievements. The last volume for "Agent Silent Death" can honestly either make or break your run if you're trying to do a full run of all three volumes on the hardest/harder difficulty. You need to take it slow in the beginning towards the end and as quiet as possible crawling through every bit of cover you see, at the end when you bust the generator... that's around the time you need to book it and kill the commander.
Timing is everything.
YouTuber "Kreeper V" has an all inclusive video over the DLC. Its honestly the shortest and easiest one of the bunch minus the last mission.
The last volume starts at "9:46."