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