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