Here is the full list of all 37 Steam Tactics achievements.
Piracy is fun but unsustainable
Acquire a flamethrower
Level up a pilot for the first time
Upgrade an item for the first time
Achieve your first victory
Upgrade an item to level 10
Upgrade an item to level 20
Upgrade a gun to level 30
Upgrade a ship to level 30
Level up a pilot to level 10
Level up a pilot to level 20
Level up a pilot to level 30
Level up Benedictus to maximum level
Level up Torgnan to maximum level
Level up Selva to maximum level
Level up Licia to maximum level
Acquire a two-star item
Acquire a three-star item
Level up all pilots to maximum level
Upgrade all guns to three stars
Upgrade all ships to three stars
Acquire all ships
Acquire all guns
Complete the first chapter
Defeat Hades
Defeat Nicholaus
Complete the second chapter
Complete all missions in the first chapter for two stars
Complete all missions in the second chapter for two stars
Complete all missions in both chapters for two stars
Complete all missions in the first chapter for three stars
Complete all missions in the second chapter for three stars
Complete all missions in both chapters for three stars
Acquire a torpedo launcher
Acquire an acid gun
Acquire a tesla gun
Light all lighthouses