Here is the full list of all 16 Amaranthine achievements.
Complete game on legend mode
Reach 20 level on legend mode
Sell 100 weapons
Complete subwarp level
Destroy 5000 enemies
Destroy the overwatcher
Complete level without taking any damage
Destroy the battlecruiser
Complete game on normal
Find legendary weapon
Destroy the bomb
Ram 50 enemies
Kill 10 enemies in 1 secon
Destroy 1000 enemies
Destroy 12 cargo ships in a single run
Destroy 250 enemies