What does "fiendish" mean?

Native speaker’s answer
Rebecca
"Fiendish" is an adjective meaning cruel, evil, vicious, or devilish. It's a very negative word used to describe people that are extremely unpleasant, unlikeable characters. The noun form is "fiend." Ex: The villain was a fiendish, evil person. Ex: The villain of the movie gets more and more fiendish as the movie goes on.