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