Here is the full list of all 28 Metal: Hellsinger achievements. It takes around 5-6 hours to unlock all of the achievements on Windows.
Destroyed the Red Judge aspect in Gehenna
Destroyed the Red Judge aspect in Incaustis
Got 666 kills (game total)
Obtained all weapons
Destroyed the Red Judge aspect in Yhelm
Destroyed the Red Judge aspect in Stygia
Destroyed the Red Judge aspect in Voke
Multi-killed 2 enemies
Reached Hit Streak: 20
Reached Hit Streak: 10
Destroyed the Red Judge aspect in Acheron
Destroyed the Red Judge aspect in Nihil
Destroyed the Red Judge
Reached Hit Streak: 35
Reached Hit Streak: 50
Completed a Torment
Achieved the top result in a Torment
Killed 50 Behemoths
Completed all Torments
Soared (Dash + jump) 100 times
Died in a Chaos Crystal explosion
Never hit off-beat in a Hell
Died 20 times
Killed 25 enemies while maintaining a Hit Streak
Killed two Seraphs in one attack
Killed 8 enemies in 4 seconds
Cleared a Hell using only Paz
Killed a Judge's Aspect with Terminus