Here is the full list of all 49 Call of Cthulhu achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Refuse the ritual
Invoke Cthulhu!
Successfully carry out the counter ritual
Chat with a vision
Open the sailor's chest in the whaling station
Enter the beast’s den
Kill 5 inhabitants who are being controlled
Kill or spare Bradley
Escape your fallen territory
Accept the revelations
Save Drake's life during the fight with the creature
Banish the creature for good
Never drink
Lay your hands on Algernon Drake's treasure
Find Sarah Hawkins
Read all the books of unholy knowledge
Fall into Fuller's trap
Meet Algernon Drake and accept his help
Learn the secret of the Scylla
Read the Necronomicon
Find occult items
Banish the Dimensional Shambler
Banish the Dimensional Shambler using only one dagger
Inspect 50 items
Accept to read an unholy book
Meet Francis Sanders
Take part in the ritual in the caves
Fall into the sacrificial pit
Discover the mansion’s secret passage
Use the globe to open the secret passage
Explore the memories of the Hawkins family
Convince the caretaker to help you
Get driven to the Hawkins Mansion
Accept the Sarah Hawkins case
Fail a skill test
Reach the level of Expert in a skill
Find 20 hidden items
Discover all the small blue bottles
Piece together Margaret Wyckwood's memoirs
Discover all the murals of the disappeared tribe
Be the plaything of an hallucination
Make a deal with a crazed inmate
Push Irene Sanders to the limit
Deliver liquor to the sailors
Save Mitchell
Make the suspects talk by using a heavy hand
Heal all the patients
Choose all the replies in R’lyehian
Refuse to take part in the ritual