hell on earth vs inferno

hell on earth and inferno both are nouns.

Word	Noun	Adjective	Verb	Adverb
hell on earth	Yes	No	No	No
inferno	Yes	No	No	No

As nouns, hell on earth and inferno are synonyms defined as:

Other synonyms of hell on earth include hell, hellhole, snake pit, the pits.

hell on earth (noun)	inferno (noun)
any place of pain and turmoil	a very intense and uncontrolled fire
	any place of pain and turmoil