Here is the full list of all 14 Delta Squad achievements.
Complete everything
Starting, complete any level
Find all the hidden loot in any level
Use your secondary weapon
Eliminate one of the bosses
Destroy a tank
Kill 100 Heavy soldiers
Kill 50 Engineer soldiers
Kill 3 enemies with a single grenade
Kill 100 Infantry soldiers
As a medic, heal yourself or heal someone else
Kill 10 enemies with a single grenade
Survive at least 5 waves in survival mode
Survive at least 10 waves in survival mode