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