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