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