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
Turned into a doppelganger
Entered ten haunters
Remembered the story of the Lost Child
Managed to hide succesfully ten times
Managed to hide succesfully five times
Found five diary pages
Touched the weeping one
Turned the light on in every room
Managed to hide succesfully
Found a diary page
Saw three fragments of reality
Saw a fragment of reality
Entered a breach
Entered a haunter
Turned the light on in a room before a breach opened