Here is the full list of all 30 Sons of Valhalla achievements.
Defeated wave 75 in Horde mode
Defeated wave 65 in Horde mode
Defeated wave 55 in Horde mode
Defeated wave 45 in Horde mode
Defeated wave 25 in Horde mode
Defeated wave 35 in Horde mode
Tutorial finished
Raya escaped
Thorald and Raya reunited
Escaped Niflheim
Loki defeated
Sailor defeated
Knight defeated
Crocodile hunter defeated
Sir William defeated
Trainer defeated
Quarry giant defeated
Little man defeated
Bloodhound defeated
Butcher defeated
Slave trader defeated
Tribal leader defeated
Bishop defeated
Graveyard keeper defeated
Priest master defeated
Fur trader defeated
Valgard defeated
Fire devil defeated
Man's best friend
Scarecrow defeated