Here is the full list of all 20 Cube Man achievements.
First training
Earn three stars on the first screen
Die for the first time
Rescue your friend on the second screen
Access the boost energizer
START SLOW MOTION
Eliminate the first boss
Fly an airplane
Fly a Jetpack
Complete the earth world
Complete the world of fire
Complete the ice world
Complete the world of limbo
Complete the toxic world
Win all bonus screens
Get three stars on all screens
Win the 11th screen in the world of the earth in less than 9 seconds
Win the 14th world screen in limbo in less than 53 seconds
Find the secret path of the 6th screen in the toxic world
Complete all bonus screens with 3 stars