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