Here is the full list of all 21 Death From Above achievements.
Neutralize 25 soldiers
Neutralize 4 enemies in a short time
Neutralize 10 soldiers
Explosion of a vehicle kills an enemy soldier
Visit all locations at the training grounds
You got defeated by a tank
Neutralize 50 soldiers
Destroy 10 tanks
You were defeated by a convict
Your drone was lost in battle
Raise all of the flags in the level
Fly through a garage building with the FPV drone
Destroy a convoy of enemy vehicles
Collect all NAFO Fella collectibles
Clear all minefields in the level
Hit the Russian drone with the FPV drone
Achieve Mission 5: Missile Rush mission without penalty
Drop a stolen washing machine on an enemy soldier