Here is the full list of all 32 Battle Nations achievements.
Kill More Than 1 Unit With a Single Attack
Construct 15 buildings
Own 2 Barracks
First Steel Mill
First Raid Mission
First Attack Mission
First Occupation Mission
10 Soldiers in Your Army
Win 25 Raid Missions
Own 25 Districts
Win 25 Attack Missions
Win 25 Occupation Missions
Defended Against 5 Consecutive Attacks
Defended Against 15 Consecutive Attacks
First Attack vs. a Friend
10 Full Garrisons
Defeat an Army of 12 in 12 moves
Defeat an Army of 12 in 8 moves
Defeat an Army of 12 in 4 moves
First Flamethrower Ignition
Bring 12 Soldiers to a Battle
Defeat an Army using only Artillery
Win 10 Battles in 10 Minutes
Play PvP With a Friend
Play PvP With Friends 100 Times
Participate in a Boss Strike while in a Guild
Earn the Tier 1 Prize in a Boss Strike
Earn the Tier 10 Prize Boss Strike
Earn the Tier 11 prize in a Boss Strike
Contribute 100 points toward a Boss Strike!
Contribute 2000 points toward a Boss Strike!
Contributed 10,000 points toward a Boss Strike!