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