Here is the full list of all 40 Deathless: The City's Thirst achievements.
Take a vacation.
Save Carver Valley.
Perform certain experiments.
Keep Dunestrider alive for the entire story
Build a relationship with Jess.
Save Zacate Town.
Preserve the Zacate Dam water supply.
Negotiate a fair treaty.
Sleep with Mezatchul.
Protect the delegation.
Save Verity Chen from the Scorpionkind.
Save the North Valley deal from the Scorpionkind.
Kill someone as early as possible.
Start a war.
Break the Scorpionkind forever.
Negotiate an advantageous treaty.
Betray a friend.
Betray your boss.
Solve the mystery of the body in the bathtub.
Solve the mystery of the locked room.
Solve the mystery of the unmarked corpse.
Solve all possible mysteries.
Kill a murderer.
You must have known this was coming.
Prosper from a conspiracy.
Get the city the water it needs.
Get the city the water it needs—without destroying Carver Valley.
You always have the choice to leave.
Join a revolution.
Perish. Expire. Join the Choir Invisible. Except you wont, because that doesn't exist.
Kill a friend in self-defense.
Let yourself die.
Try something new.
Build a relationship with Verity Chen
Sleep with Caspar Jones.
Talk poetry with a deathless king.
Talk poetry with a deathless king above the wreckage of a war you caused.
Sleep with Verity as early as possible.
Sleep with Jess as early as possible.
Find peace.