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