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