infernal vs hellish

infernal is a noun but hellish is not a noun.

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

As adjectives, infernal and hellish are synonyms defined as:

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

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

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

infernal (adjective)	hellish (adjective)
being of the underworld	extremely evil or cruel; expressive of cruelty or befitting hell
characteristic of or resembling Hell	(informal) very unpleasant
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