infernal vs demonic

infernal is a noun but demonic is not a noun.

Word	Noun	Adjective	Verb	Adverb
infernal	Yes	Yes	No	No
demonic	No	Yes	No	No

As adjectives, infernal and demonic are synonyms defined as:

infernal and demonic: extremely evil or cruel; expressive of cruelty or befitting hell

Other synonyms of infernal include diabolic, diabolical, fiendish, hellish, satanic, unholy.

infernal (noun)	demonic (noun)
an inhabitant of Hell

infernal (adjective)	demonic (adjective)
being of the underworld	extremely evil or cruel; expressive of cruelty or befitting hell
characteristic of or resembling Hell
of or pertaining to or characteristic of a very uncontrolled and intense fire
expletives used informally as intensifiers
extremely evil or cruel; expressive of cruelty or befitting hell