Here is the full list of all 43 Mr. Bree+ achievements.
Get all other achievements
Complete all levels in all game modes
Beat 40 levels in hardcore mode
Beat 20 levels in hardcore mode
Beat 5 levels in hardcore mode
Start a level in hardcore mode
Skip the last cutscene
Beat all levels without dying
Watch the credits cutscene to the end
Defeat the slaughterhouse boss
Press the red button!
Get 75% of all achievements
Beat level 24 in less than 29 seconds
Collect all bad memories
Defeat the forest boss
Beat 40 levels without dying
Beat your best time 20 times
Beat your best time 10 times
Beat 40 levels
Collect 20 bad memories
Perform your first double jump
Get Double Jump
Get 50% of all achievements
Die on the first level
Die 100 Times
Beat 20 levels
Beat 20 levels without dying
Die 10 times in the same level
Die 50 Times
Beat the tenth level
Collect 5 bad memories
Get Run
Stay still for a while
Die 5 times in the same level
Enter the first slaughterhouse level
Beat 5 levels
Beat 5 levels without dying
Get Crouch
Quit a level
Collect the first bad memory
Die 1 time
Get Jump
Get Wall Jump