Here is the full list of all 51 Gabriel Knight: Sins of the Fathers 20th Anniversary Edition achievements.
Complete with game with a full score of 362 points
Don't try to save Malia
Enter the ceremony alone
Compliment Gran as thoroughly as she deserves
Exhaust Dr. John on the topic of Voodoo
Complete the game with less than 362 points
Complete Day 10
Try to save Malia
Enter the ceremony with back-up
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
Complete Day 3
Have a fated run-in
Make a jewelry mold
Find Madame Cazaunoux's address
Have your fortune told
Sit through the Voodoo lecture
Complete Day 2
Excessive flirting!
Get a copy of the Voodoo Murders File
Obtain a false ID
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