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