Here is the full list of all 11 Bad North: Jotunn Edition achievements worth 1,000 gamerscore.
Completed the campaign on any difficulty
Won an island in the snow
Killed 1000 vikings
Fully upgraded one of your commanders
Won 10 islands in a row, without losing a single house
Killed all the vikings in a ship, before it reached the shore
Purchased an upgrade for one of your commanders
Complete the campaign on hard, recruit all commanders and keep them alive
Kill 15000 vikings
Win an island at nighttime
Win 3 islands on a single turn