hell on earth vs hellhole

hell on earth and hellhole both are nouns.

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

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

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

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