Here is the full list of all 52 Left-Hand Path achievements.
Defeated the lurker in Nehemoth
You retrieved hidden lore in Nehemoth
You successfully channeled the power of magic into a spell.
Overcame Sathariel's greatest challenge
You have learned all there is to know of the events in Nehemoth
You retrieved hidden lore in Sathariel
You learned all rituals in the first Early Access release
You have learned all spells in the first Early Access release
The Well's inhabitants defeated you 5 times.
You learned some of the reason why Elena is here.
You have defeated 100 of the Soulless in combat.
You freed Julia from her trap.
You traveled from the first head to the end of Sathariel having taken no damage. Please feel free to message the dev and tell him how you did it!
You have learned all rituals - including that one most forbidden - in the Well up to the end of Gamichicoth
You have learned all magical workings in the Well up to the end of Gamichicoth
You have killed more than 100 of Those That Crawl From Below in Gamichicoth
You have destroyed more than 50 of The Hidden Whisperers in Gamichicoth
You have defeated the First Of The Three in Gamichicoth. Your luck grows...
You have defeated the Second Of The Three in Gamichicoth. Your wrist becomes stronger...
You have conquered the Third Of The Three in Gamichicoth. Now you may feast...
You have defeated the ultimate threat in Gamichicoth.
You have... acquired all the staves available to you in Gamichicoth
You have learned more of Elena's journey and purpose in the Well.
You have learned the hidden magick available to you in Gamichicoth
You have passed from Gamichicoth and into the lands beyond.
You understand Jared, as much as anyone does.
You managed to get from the start to the end of Gamichicoth without taking any damage. Feel free to message Hugh and tell him how you did it!
You have survived casting Raishyud, whether by luck, uncommon skill, or dark bargain.
It appears that you have learned intelligent caution in the Well...
You have proven considerably harder to kill than certain parties expected.
You have discovered all recent events and tales from Sathariel.
Of Gamichicoth, its inhabitants and its woes, you know as much as any person.
You amused the Angel of Samael
You availed yourself of an efficacious concoction
You were found to be uncommonly stubborn
You have learned all the magical workings of the Well
You have learned all the rituals of the Well, including the Greatest.
Defeated Adremalech, the Angel of Death
You killed the Angel of Death, despite the consequences.
Made an unexpectedly merciful choice, for whatever reason.
You spared Marcus his fate, despite the cost.
You avenged Jill and Tom, despite the cost.
You have learned the hidden magick available to you in Samael
You fed on the husks of all the Quislings in hiding in Samael
The Screaming Heads refused you more power even in Samael or Xanadu
You learned the full story of the Solider of Samael
You learned the full story of the Returnee of Samael
You've learned the story of Coleridge's Magical Poems
You've learned all there is to know of the intertwined stories at the end of the Well.
You've killed more than 25 of the nameless nightmares that hiss and stalk the dark parts of Samael
You have reached the end of this branch of the Left-Hand Path. Congratulations.
You've gone from the start to the end of Samael and taken no damage. Feel free to message the dev and explain how you did that!