This free DLC has a full achievement list, and I wanted to clear all of it. I wrote this guide so you can do the same without wasting time on the ones that are easy to miss. I do not speak English well, so I used a translator here. If any achievement name or word looks slightly off, that is why.
Most of these unlock naturally as you play. A few need specific setups. The list below goes through every one, from the simple to the annoying, and I point out where you can stack several at once.
Abstainer
The easiest one on the list. Just finish the level without pressing the button that activates slow-motion. Almost everyone has this one.
Sweet Dreams
Walk up behind an enemy and choke them out. That is the whole thing.
Clenching Cheeks
Complete the level without saving. This one is a bit trickier. I did it on the True difficulty setting. You could try to sneak through the first level, though you will probably get spotted. I just killed everyone right away, and that worked for me.
Poltergeist
Stun an enemy with a heavy object. Find a brick in the level and throw it at an opponent.
One thing I learned here: a brick makes it very easy to clear levels undetected. Keep that in mind, because it helps with several later achievements.
Straight Edge
Complete the entire campaign, not just one mission, without using slow-motion. There are only two missions in the game. I think it is very easy to beat both without slow-motion at all.
Allergic to Pain
Complete a mission without taking any damage. You can pair this with Stealthy and Dangerous below. That is the simplest way to get it.
Knock-Knock
Kick down a door so it knocks out the enemy standing behind it. This is not hard. For a stealthy version, memorize one enemy’s patrol route, stand behind the door in their path, and kick when they walk through.
Accept the Challenge
Complete the campaign on the True difficulty setting. This should not give you major problems. If you cannot just gun everyone down in open combat, try a stealthy approach. It is slow, but it works.
Opportunist
Neutralize an enemy while they are affected by a flashbang. When the mission loads, grab a grenade and toss it at the feet of the first enemy you find.
Death Metal
Kill an enemy with a fragmentation grenade. Same method as Opportunist: grab a grenade and use it on an enemy.
Friendly Fire
Throw a flashbang into a crowd of enemies so one of them fires wildly and kills one of their own. Do the same thing as Opportunist, but throw into the crowd and wait. Save before you throw, and reload if it does not happen.
Sniper
Kill five enemies in a row with headshots. Before the mission, equip the BET VP9 pistol (the in-game text is pixelated, but this is the pistol with the built-in silencer).
To make sure your character hits the head, aim at the enemy by holding the right mouse button until the head icon appears. Then take out five enemies in a row, staying stealthy.
Ghost
Complete the level without being detected. This is the one where I want you to pay close attention. If you run into an enemy and they spot you, even if you take them down before they fire or raise the alarm, it still counts as detected.
So either go around the enemy, or do this together with Stealthy and Dangerous. In that case, I suggest bricks for enemies that are hard to reach.
Pacifist
Complete the level without killing anyone. You can also do this while going for Stealthy and Dangerous. Walk past enemies, or knock them out with your fists or bricks. A tranquilizer as your primary weapon and a taser as your secondary weapon also work well.
Stealthy and Dangerous
You can stack a bunch of other achievements with this one. Neutralize all enemies on the level without being detected.
Same warning as Ghost, and it matters: if you walk in front of an enemy and they spot you, even a fast knockout counts as being detected. Either bypass the enemy or combine this with the right gear. Bricks help for hard-to-reach enemies.
About whether you are allowed to actually kill the enemies, I am not sure. I did this one as a pacifist.
True Pacifist
Complete the entire campaign without killing anyone. For gear, use a tranquilizer, a taser, and empty magazines to create noise. You will not need body armor.
The first mission can be done by simply bypassing everyone. In the second mission, you must either kill or knock out every enemy. Watch the patrol routes, memorize them, and catch enemies off guard. There is no step-by-step route I can give you here. It is up to you, but it is nothing too difficult.
Mass Hypnosis
Stun five enemies with a gas grenade. This is where it gets tricky. Gathering five of them in one spot at once is hard.
Here is how I suggest you do it. Load the last level. Equip something loud as your primary weapon and a gas grenade. Leave the starting building and go left. You will hit a wall with a vent. Shoot into the air to lure enemies in, then immediately equip your grenade and enter the vent. When you see a large group of enemies, climb out and throw it. If the enemies do not come to you, shoot into the air again and go back into the hatch.
Arsonist
This one is even easier than the last. Set five enemies on fire at the same time. You could do the hatch method again, but why make it complicated?
Load any level, grab a Molotov, and stun five enemies while keeping them alive. Pile the bodies together against a wall and throw the Molotov at them. That should unlock it. This worked in the previous game, so it most likely works the same way here.
Delivery Failed
Throw back a grenade that an enemy tossed at you. Patience is the key here.
Load the final level. Kill about 10 enemies. Save your game near the starting building and wait for an enemy to start lobbing grenades at you. If it does not happen, reload your save. The important part is to save close to where the enemies are clustered.
You also need to keep reminding the enemy where you are. Step into their line of sight to trigger gunfire, then quickly retreat to nearby cover. In short, bait them into throwing a grenade.
Hot Potato
Similar to Delivery Failed. Throw back an enemy grenade so that it kills someone. The actions are exactly the same.
Paparazzi
Throw back an enemy flashbang so that it blinds an opponent. Again, the actions are the same as Delivery Failed.
Conclusion
The long list looks intimidating, but a lot of it overlaps. Plan your runs around stacking stealth achievements, and the rest will follow. Good luck with the throw-back grenade ones, those took the most patience for me.
