demonic
adj.adj. describing something that is very evil, cruel, or scary, like a demon. You can also use it to describe someone who has a huge amount of wild energy.
adj. relating to or characteristic of a demon; manifesting extreme cruelty or supernatural evil. Often used figuratively to describe intense, frenetic, or seemingly superhuman energy.
The villain in the movie had a demonic laugh.
The athlete played with a demonic intensity that left his opponents struggling to keep up.
The old legends spoke of a demonic presence haunting the woods, though modern scholars interpret these tales as metaphors for the psychological terrors of isolation.
From Latin daemonicus, from Ancient Greek δαιμονικός (daimonikós, “possessed by a demon, sent by a demon”), from δαίμων (daímōn), equivalent to demon + -ic. Doublet of daimonic.
Often used figuratively to describe human behavior or energy levels rather than literal spirits.