Here is the full list of all 15 Risk of Rain achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Drown 20 Whorls.
Die 50 times.
Find the robot janitor.
Find the bloated survivor.
Bank 20,000 gold.
Deal 5000 damage in one shot.
Collect 15 Monster Logs.
Unlock a golden chest with the Explorer's Key.
Collect 4 Keycards.
Kill a boss with 'Lights Out'.
Fail a shrine 3 times in a row.
Survive 40 minutes.
Pass a shrine 4 times in a row.
Kill the Magma Worm, Wandering Vagrant, and Giant Stone Golem.
Defeat 20 lemurians in one playthrough.