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