Here is the full list of all 16 Agent 9 achievements.
Pulled the big red lever
All sneaky beaky like
Defeat 15 Goons
Completed the theme-establishing walking simulator
A participation trophy
It's not rocket science
That's no telescope
Defeat 10 Sentries
Defeat 15 Drones
Defeated the Codex
23 didn't make it, but he was onto something...
Don't you know not to press big red buttons?
It aint over yet
Completed Chapter #1 on Permadeath Mode
Completed Chapter #1 on Casual Mode
Cracked the code