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
Soared (Dash + jump) 100 times
Never hit off-beat in a Hell
Died 20 times
Killed a Judge's Aspect with Terminus
Destroyed the Red Judge
Obtained all weapons
Died in a Chaos Crystal explosion
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
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
Cleared a Hell using only Paz
Multi-killed 2 enemies
Reached Hit Streak: 50
Reached Hit Streak: 35
Reached Hit Streak: 20
Reached Hit Streak: 10