Here is the full list of all 28 The Sinking City achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Kill the archeologist.
Study all the frescoes in the Temple of Dagon.
Dethrone the patriarch.
Challenge the horror of the Redemption Church.
Humor a grieving mother.
Go below the surface for the first time.
Agree to the experimental treatment.
Use the intelligence archives in your investigation.
Give an interview to the local newspaper.
Solve your first case in Oakmont.
Have your fortune read.
Press the button.
Betray the warehouse guard's trust.
Help the professor with his plan.
Punish the upstart.
Ask the Imperial Wizard to show you a magic trick.
Have a ritual conducted on you.
Kill the old lady.
Finally commit the crime you were accused of.
Kill the priestess.
Defeat a little girl without playing fair.
Prevent the last self-immolation.
Leave the city and the world to their fate.
End the Cycle.
Restart the Cycle.
Take Sidney's stash. You monster.
Uphold your agreement with Robert.
Complete every challenge Oakmont has to offer.