Here is the full list of all 10 Steel Empire achievements.
Clear Stage 1 (regardless of difficulty)
Clear Stage 2 (regardless of difficulty)
Clear Stage 3 (regardless of difficulty)
Clear Stage 4 (regardless of difficulty)
Clear Stage 5 (regardless of difficulty)
Clear Stage 6 (regardless of difficulty)
Clear Stage 7 (regardless of difficulty)
Defeat the true final boss.
Clear the game with the difficulty "Very Hard"
Unlock all the in-game achievements.