Here is the full list of all 21 Mad Father achievements. It takes around 5-6 hours to unlock all of the achievements on Windows.
Unlock image: "Mother's Portrait"
Unlock image: "It's Behind You"
Talk to the muttering old man
Examine the specimens in the second-floor basement
Read the New Text on Anatomy
Give the pendant to mother's corpse
Help the eyeless girl
Rescue the corpse from prison
Help the hungry boy
Read Maria's diary
Rescue the large man
Receive a present from the mysterious plant
Give the dog a bone
Get chased by father
Unlock image: "Charm Of Happiness"
See Bad Ending 1
See Bad Ending 2
See the True Ending
See the "If" Ending
Read mother's love letter in the second week
Unlock a secret event...