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