Here is the full list of all 40 The Forgotten City achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Die from hornet stings
Intimidate the creator of The Golden Rule
Reach Ending 4 of 4
Talk your way through every possible confrontation
Confront the creator of The Golden Rule
Have Duli released from his cell
Steal 2000 coins after the Golden Rule is broken
Enter a villa with a daring leap
Loop through time ten times
Trigger The Golden Rule by stealing 5 times
Solve Vergil's problem
Reach Ending 1 of 4
Save Ulpius's life
Dodge 3 boulders
Find all three missing persons
Discover Underworld icons Sisyphus, Tantalus, Ixion and the Belide
Learn the true identity of the stranger by the river
Help Galerius romance Equitia
Reach Ending 2 of 4
Enter the upper cistern in an unconventional way
Find treasure using the golden bow
Survive the Palace
Topple 10 peeled statues by kicking others into them
Gild your first thing
Lie 10 times
Discover what lies beneath the city
Read 10 different grafitti
Get rejected by Aurelia
Pick up the sponge on a stick
Save Fabia's life
Save Iulia's life
Allow Fabia to die in the collapsing temple
Loop through time once
Skip the city tour
Use Photo Mode
Reach Ending 3 of 4
Free the captive and shoot her captor with your gun
Finish the game without looping through time once
Reach the best ending with the smallest number of loops
Assemble as many people as possible in the Museum