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