Here is the full list of all 36 Sniper Elite: Zombie Army 2 (DE) achievements.
Kill 5000 enemies
Kill 2000 enemy grunts in co-op
Defeat 100 ignited zombies
Kill 20 Elites in co-op
Kill 20 Snipers in co-op
Successfully complete Chapter 5 with 4 players
Successfully complete All Chapters 4 players on Elite Difficulty
Successfully complete Chapter 4 with 4 players
Kick 50 enemies down in co-op
Successfully complete Chapter 3 with 4 players
Defeat 20 Summoners
Get at least 20 for 1 explosive kill in 4 player co-op
Successfully complete Chapter 2 with 4 players
Defeat 10 Fire Demons
Successfully complete Chapter 1 with 4 players
Get at least 10 for 1 explosive kill in 4 player co-op
Get at least 15 for 1 explosive kill in 4 player co-op
Get a 5-for-1 kill with any sniper rifle
Defeat the Final Boss
Collect all Gold Bars
Find and shoot all the bottles of blood
Kill the trapped Elite
Kill 100 skeletons with explosives
Kill any 100 enemy with the shotgun
Pick up a phone
Defeat 500 enemies with headshots
Pick up a shotgun
Kill a suicide grunt by hitting his grenade
Kill 1000 enemies
Loot an Elite's corpse
Kill 20 enemies as they revive
Defeat a Fire Demon
Kill 500 enemy grunts
Become possessed
Pick up the Preacher
Own 2 Nazi Zombie Army games