The Sacred and the Profane/Nightmare Fuel

"I'll give you ten seconds," said Zirah. His eyes were lit with bright, childlike delight.
He leaned towards Hastur, who was rapidly backing away from the enthrallment on Zirah's face.
Ligur had forgotten about stealth and was fleeing, crashing through bushes and tripping over
tombstones.
"Run," Zirah whispered. Someone yelled behind him. None of them noticed.
The figures of the two demons blurred and vanished.
The problem with this Earth, Zirah thought, was that nobody ever let him relax.
He followed them.

Reading this immediately after Good Omens itself is extraordinarily disturbing, because you know that this isn't the way things should go; please God make it stop, but it doesn't stop and in this story, this is the was it goes.
Most painful might be the dichotomy between Aziraphale, who insists on helping people he has to hypnotise, and Zirah, who happily kills babies.