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