Here is the full list of all 11 Bad North achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Win an island in the snow
Win an island at nighttime
Kill 1000 vikings
Kill all the vikings in a ship, before it reaches the shore
Win 10 islands in a row, without losing a single house
Purchase an upgrade for one of your commanders
Complete the campaign on any difficulty
Complete the campaign on hard, recruit all commanders and keep them alive
Kill 15000 vikings
Fully upgrade one of your commanders
Win 3 islands on a single turn