Here is the full list of all 20 Völgarr the Viking achievements.
Kill 4 enemies with a single charged spear attack
Block a projectile with the shield while in the air
Wield the fire sword
Unlock Mjolnir's power
Defeat the Lizardmen King
Break the Magic Seal on Fafnir's Tower
Complete the game and earn Ending C
Complete the game and earn Ending B
Complete the game and earn Ending A
Block an attack with the shield while on a rope/chain
Hitch a ride on a spear attached to an enemy shield
Obtain a Warrior Spirit
Collect a golden walrus statue
Reach the alternate path for any world
Find a Key Stone
Kill Fafnir before he reaches his Dragon form
Reach Yggdrasil's roots
Complete any world without ever losing any equipment
Complete any world in 4 minutes or less
Complete the game with 10 or less retries (deaths)