Here is the full list of all 51 Gabriel Knight: Sins of the Fathers 20th Anniversary Edition achievements.
Enter the ceremony with back-up
Try to save Malia
Don't try to save Malia
Complete Day 10
Complete with game with a full score of 362 points
Complete the game with less than 362 points
Enter the ceremony alone
Enter the secret Voodoo Hounfour
Complete Day 9
Get past the mummies like a true adventurer!
Collect all the tiles
Complete Day 8
Complete your research
Open a secret door
Complete day 7
Complete the intiation ceremony
Discover a shocking loss
Have a long chat with Wolfgang
Complete Day 6
Leave your own Voodoo code message
Decode the rada drum message
Hide the tracker
Get inside Mosely's Office
Complete Day 5
Change Mosely's mind about the Voodoo Murders Case
Translate a mysterious code
Take in a snake dance performance
Survive the deadly python
Read Gunter's journal
Complete Day 4
Witness a chilling death
Help Sam improve his game
Make a large purchase from Willy
Find the secrets of Granddaddy's Clock
Compliment Gran as thoroughly as she deserves
Complete Day 3
Have a fated run-in
Make a jewelry mold
Sit through the Voodoo lecture
Have your fortune told
Find Madame Cazaunoux's address
Complete Day 2
Excessive flirting!
Exhaust Dr. John on the topic of Voodoo
Obtain a false ID
Get a copy of the Voodoo Murders File
Complete Day 1
Find a clue at Lake Pontchartrain
Meet Malia Gedde
Get rid of the cop in Jackson Square
Read the Paper on Day 1