Here is the full list of all 31 Spectator achievements.
You have completed Backrooms on Normal
You have completed Asylum on Normal
You have completed Forest on Normal
You have completed Paranormal House on Normal
You have completed Factory House on Normal
You have completed Backrooms on Hard
You have completed Asylum on Hard
You have completed Forest on Hard
You have completed Paranormal House on Hard
You have completed Pizzeria on Normal
You have completed Pizzeria on Hard
You have completed Factory House on Hard
You have completed Backrooms on Nightmare
You have completed Asylum on Nightmare
You have completed Forest on Nightmare
You have completed Pizzeria on Nightmare
You have completed Paranormal House on Nightmare
You have escaped the Facility
500 Reports Send!
Who did that?
Shortcut to the Backrooms
That chair moved?
You don't know the answer
Disturbing Leaf
Someone in the wood
Pizza's Back!
Uncomfortable
It's just impolite
Ghost orbs spotted
Big buttons
My favorite train toy