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