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