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