Definitely not on the side of the angels (8)

I believe the answer is:

diabolic

(Other definitions for diabolic that I've seen before include "Extremely cruel" , "Fiendish and cruel, like Old Nick" , "wicked" , "Of the devil" , "Satanic" .)

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.