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.
Deal 5000 damage in one shot.
Die 50 times.
Find the robot janitor.
Bank 20,000 gold.
Collect 15 Monster Logs.
Collect 4 Keycards.
Kill a boss with 'Lights Out'.
Unlock a golden chest with the Explorer's Key.
Find the bloated survivor.
Survive 40 minutes.
Pass a shrine 4 times in a row.
Kill the Magma Worm, Wandering Vagrant, and Giant Stone Golem.
Fail a shrine 3 times in a row.
Defeat 20 lemurians in one playthrough.