Here is the full list of all 33 Zombie Vikings achievements.
Kill an enemy with their own projectile
Make an enemy bounce on 4 others
Have 6 enemies stunned at the same time
Revive a friend by throwing both parts into each other mid-air
Defeat an enemy by throwing a friend's head into them
Catch the same enemy three times without them touching the ground
Keep an enemy airborne for 4 seconds
Strike a frozen enemies back and forth 10 times
Have all players hold an enemy before it touches the ground
Get revived 50 times
Have the crushers defeat 10 enemies
Have Beaknose defeat 10 enemies
Clear the Tavern Brawl in Richside unscathed
Kill an enemy by throwing a chicken at them
Hit a frozen enemy into 5 other enemies
Win a duel to the undeath
Defeat a boss with zombie vomit
Perform the 4 player charge attack on the stitch zombie
Kill 3 heavy enemies at the same time
Find the super secret developer area
Form a zombie tower of 5 with a guest of your choice
Escape the fishturd cannon unschathed with 4 players
Win against the Butterflies in Söcker without letting the other team score once
Complete the secret Fe dream sequence
Complete the gnome cave without ever being detected
Spend a total of 30.000 gold in the store
Defeat the Common Cold without hitting him with your sword
Finish the Berzerker Factory without one player touching a conveyor belt
Finish the story!
Unlock all weapons
Unlock all runes
Complete all sidequests in the game
Open 25 chests