Here is the full list of all 23 Clockwork achievements.
Use a Portal
Die 5 times in one level
Die during the Act 1 Boss Fight
Solve a Puzzle with a Shamblebot
Control Milli
Solve a Puzzle using a Time Remnant
Finish the First Level
Play the Game
Play the Game for Two Hours
Finish Act 01
Finish Act 02
Finish Act 03
Finish the Game in One Session
Beat the First Boss without Dying
Beat the Final Boss without Dying
Die during the Act 3 Boss Fight
Kill a Shambler
Solve a Puzzle with a Box
Solve a Puzzle with a Sentry
Idle for 5 Minutes
Place a Portal
Fix a Leg
Fix the Generator