Here is the full list of all 15 IronKnight achievements.
Destroy 50 enemy ships in one battle
Destroy 100 enemy ships in one battle
Destroy 1000 enemy ships in one battle
Enter the battle 10 times
Enter the battle 100 times
Destroy 1 boss-class ship in one battle
Destroy 10 boss-class ship in one battle
Destroy 10 boss-class ship in total
Destroy 50 boss-class ship in total
Destroy 100 boss-class ship in total
Get 1000 points in one battle
Get 5000 points in one battle
Get 10000 points in one battle
Unlock all helicopters
Unlock all supports