Sniper Elite V2 Remastered

Note: It is possible to unlock this achievement and Smoking Kills (10G) in the same playthrough.
 
To play this mission: Single Player > Challenge > Neudorf Outpost. Note that you cannot play this mission in co-op. It is recommended that you select the Welrod in your loadout before attempting this achievement.
 
You can change the difficulty to Custom and it will not void the achievement since this mission is not considered a part of the main campaign. Recommended settings are:
 

• Difficulty: Custom
• Enemy Skill: Rookie
• Ballistic Realism: Simple
• Tactical Assistance: Full

This and Secret Service (25G) are probably the two most difficult achievements in the game aside from Sniper Elite (100G) because of the uncertainty of enemy placement, the need to be 100% stealthy and the lack of/sparsity of checkpoints. You need to complete the mission completely undetected but do not have to kill every enemy, although making sure live ones are tagged is suggested so you can always keep track of them.
 
Enemy placement is somewhat randomized, but are generally in the same locations each time. Depending on your speed and path throughout the mission, they might not be in the same location each time. It is recommended that you keep a mental note of how many you’ve killed in each section.
 
Here is an enemy breakdown for each section. This is what I personally encountered, so be very careful as there may be more!
 

• Upper Section - 6-8 enemies (1 in sniper nest [smoking], 1-2 in bunkers [at least one smoking], 4+ on patrol [one near starting point [smoking], one walking in front of bunkers, one near sniper tower, one past bunkers])
• Lower Section - 7-9 enemies (1 at the top of the big structure dividing the sections, 1 in the northern-most sniper nest [smoking], 1 walking the western wall [smoking], 1 outside the small center building [smoking], 1 patrolling near the small center buildings [smoking], 1 patrolling near the center sniper nest, 1 outside the southern-most larger building [smoking], 2-3 inside the structure dividing the sections [you do not need to go in there]

Unless you are close enough to an enemy to use your Welrod, to stay undetected, you need to wait for sound masking before firing your primary weapon (it is not recommended you use your secondary weapon at all). Sound masking occurs approximately every 10 seconds so you will need to be patient. This is not a mission you do quickly.
 
Enemies can spot bodies, but that’s about it. If they do, they will be more aggressive in their search and thus more likely to detect you. If they see or detect you in any way, including hearing footsteps or throwing rocks, this voids the achievement (unless you’ve reached one of the two checkpoints in the mission). It is recommended that you hide bodies whenever you have the opportunity, especially in the lower section before you obtain the C-4.
 
As mentioned, there are only two checkpoints in this mission; when you pick up the C-4 and after you plant the third explosive, both in the lower section. If you are detected at any time after reaching either checkpoint, simply reload them. If you haven’t reached a checkpoint yet and are detected, you need to restart the entire mission.
 
Once you obtain the C-4, a truck with 5-6 enemies will drive up from along the western edge of the map and park just inside the west gate in the lower section. If you did not hide bodies as mentioned above, the truck enemies will find them and search. But, you do have time to plant the three explosives and leave the section before they park, so do that as quickly as possible. Once you plant the third explosive, you will trigger another checkpoint and two trucks with 6-7 enemies will appear at your starting point. As you make your way closer to the exit, be careful and watch them split up before taking them out. Looking at the starting point, you only have to worry about 3-4 enemies from the leftmost truck as that is the one blocking your exit. Take it slow and you shouldn’t have too many issues.
 
For further reference on this achievement, there was a Steam guide written by the Winter Warlock in 2016 based on the original release of this DLC in 2012. It details a good amount of information about this mission and enemy placement. You can find the guide HERE.
 
Thanks to 360GameTV for the video:

Thanks to Dazefex Gaming for the video: