Demonic

[Dave Paprocki]

Of or pertaining to a demon or to demons; demoniac.

[Little_Girl]

Evil, in a manner of speaking. In reality, most who have been described as Demonic are usually just lonely and in need of love. Or it could just be that they are 7 ft tall, wear a cape and have glowing [red eyes]. And eat people.
When an inanimate object, such as a film or [potted plant] is described as [demonic], the term often means evil, dark as hell, or sickly twisted. This is only in context though. It could be you are referring to the pot planbt of a Mr. Bee El Zebub.