The scariest King's passage for me is (expectedly) in Pet Sematary; I can't quote it verbatim because I am home alone, and the night is coming - I prefer not to touch this book under such circumstances. It's when

Spoiler:
He is waiting for Gage to come back, and hears a sound in the house. The sound is stealthy, but at the same time it's obvious that the one who made it meant it to be heard.


I really wish I hadn't remembered it now.