Here is the full list of all 35 Lovecraft's Untold Stories achievements.
Complete the stories of every playable character on HARD difficulty
Defeat every Great Old One with the same character
See what was impossible to see
Defeat Azathoth
Save the Earth from the Great Old Ones
Defeat Nyarlathotep
Collect 100% of the information of all the Great Old Ones
Find every mini-event
Find 75% of the mini-events
Complete all the side quests
Complete the story of the Ghoul
Defeat Shub-Niggurath
Defeat Cthulhu
Make every playable character go crazy, at least once
Complete the story of the Thief
Collect 100% of the information of one of the Great Old Ones
Get 5 curses of the Great Old Ones at the same time
Unlock the Ghoul
Complete the story of one playable character on HARD difficulty
Complete the story of any playable character without using the shops, and expelling them if you see one
Complete the story of any playable character without receiving any curse
Complete the story of the Witch
Defeat Dagon
Complete any Great Old One location without having 100% information about it
Unlock the Thief
Complete the story of the Professor
Find things not from this world
Eat 100 chocolate bars
Spend 100,000 dollars and 100,000 information in the magazines
Unlock the Witch
Find a secret room without the Detective
Complete the story of the Detective
Make 1 playable character go crazy, at least once
Unlock the Professor
Die in a strange place