hellhole vs hell on earth

hellhole and hell on earth both are nouns.

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

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

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

hellhole (noun)	hell on earth (noun)
any place of pain and turmoil	any place of pain and turmoil