Here is the full list of all 18 Knock-knock achievements.
Chose to lock The Lodger inside the cabin and remain hidden
Chose to go into the woods
Saw all fragments of reality
Managed to hide succesfully ten times
Remembered the story of the Lost Child
Found five diary pages
Found a diary page
Turned into a doppelganger
Touched the weeping one
Entered ten haunters
Entered a breach
Managed to hide succesfully five times
Saw three fragments of reality
Turned the light on in every room
Turned the light on in a room before a breach opened
Entered a haunter
Saw a fragment of reality
Managed to hide succesfully