Since most of the kill/grenade/explosives achievements can be easily obtained by simply playing through the game or custom missions I'm not going to go into detail about those.

Instead this guide will focus on the two harder-to-get (due to bug 'fixes') achievements that I wasn't able to find a proper guide or walkthrough for, namely:

Communication Terminated

You have managed to destroy communication device without being detected on your way to Soltani's hideout


Silent Threat

You have completed a mission without firing a single shot

You have managed to destroy communication device without being detected on your way to Soltani's hideout

Bug fixes
In the early stages of the game, you could just walk up to the first guard, stab him, then continue on your way to the comms device with the right timing of enemy patrols. However, the 'fixes' made it impossible to sneak towards the first enemy, and the patrols stopped, so the enemies will mostly stand in place, pretty much always looking towards your approach.

4 Sniper rifles with Scope and Silencer Upgrade
(If you lack the funds, have a look at my guide for farming XP and Credits quickly)
Note: This will work with any Operator skill level, I reset every Operators' skills to confirm

This is pretty obvious and straightforward now, but if you run into trouble, here's a short walkthrough.



In the main menu, select New Mission -> Operation Tempest -> Connection Lost








Equip all of your Operators with Sniper rifles, attach silencers and move them into position as shown in the screenshot.







Kill the guard in the watchtower, end your turn, then kill both enemies at the gas station.








Move up to the guard at the exit from your spawn, stab him, then align your Operators next to the car. (The encircled guard will either move between the 3 positions marked with red or spawn at the blue circle.)





If he's on the roof, just wait for him to take one of the positions closer to you, then shoot both guards.
If he spawned downstairs, just kill the guard on the roof, advance your Operators downwards (as indicated in the screenshot), then finish him off.





Now you can safely move up to and through the building towards the comms device in the back of the house.

You have completed a mission without firing a single shot


Phrasing, because what the description should spell is:

You have completed a mission without a single shot being fired

This means not only are you not allowed to fire a weapon, neither is the enemy, so you can't simply choose a mission and run up to the enemy to stab them and then just heal the damage you take, because you will eventually get interrupted and fired upon. Luckily, usage of grenades and explosives is permitted, so we will utilize those instead (actually only grenades)

2 grenades
'African Town I' availabe for custom missions
Note: This will work with any Operator skill level, I reset every Operators' skills to confirm




In the main menu, select New Mission -> Create Mission and choose Type: Hold Position and Map: African Town I







At mission start, make sure the Operator closest to the underpass (Ian in the screenshot) as well as at least one other Operator has a grenade.







Move that Operator as far as possible into the underpass and the other three into or as close as possible to the building on the right.







At the beginning of you next turn, throw a grenade towards the corner of the left building.








In the same turn, move that Operator to the corner of the right building...








...and send the other three into the same building.









Move the last Operator from the corner into the building, then skip four turns.








Now send the Operator with the second grenade to the right side of the door and throw a grenade so that it lands directly in front of the door where the group of enemies is.*




*Try and aim at the spot as shown in the screenshot, as the grenade will bounce a bit further and there is an additional enemy still hidden in the building.