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