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