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