Here is the full list of all 31 Achtung! Cthulhu Tactics achievements.
Have characters use 3 limited use items in a turn
Do all missions in a single campaign
Complete the campaign
A character is missed by 5 attacks in the same turn
Throw 20 grenades
1 player Character kills 3 more enemies in a single turn
Have 1 character use 6 Momentum in a single turn
All allies suffered from a Psychological Effect this turn
Kill 200 enemies overall
Have 3 characters damage a single target without killing it
Take a gun from full mag to empty in a single turn
All allies are staggered at the same time
Kill 100 enemies overall
Kill an unrevealed enemy
Hit 3 enemies in a single explosion
Kill an enemy dealing 10 points more than their current HP
Kill an enemy due to the bonus critical hit damage
Complete a mission without taking any damage
Completed the whole Tutorial mission (with Tutorial active)
Complete a side mission
Have 3 characters Incapacitated and pick one up with Stay With Me
A character is hit by 5 attacks in the same turn without being rendered unconscious
Kill a Shoggoth section entirely surrounded by other Shoggoth sections
Complete all main and side objectives in main missions
Complete a mission with all characters having been rendered Incapacitated at least once
Complete a mission with at least 1 character not dealing any damage
Take each item on a mission
Take each mod on a mission
Use 10 medkits
Collected all other achievements
Completed the game on Mythic difficulty