gruelling vs backbreaking

gruelling and backbreaking both are adjectives.

Word	Noun	Adjective	Verb	Adverb
gruelling	No	Yes	No	No
backbreaking	No	Yes	No	No

As adjectives, gruelling and backbreaking are synonyms defined as:

gruelling and backbreaking: characterized by effort to the point of exhaustion; especially physical effort

Other synonyms of gruelling include arduous, grueling, hard, heavy, laborious, operose, punishing, toilsome.

gruelling (adjective)	backbreaking (adjective)
characterized by effort to the point of exhaustion; especially physical effort	characterized by effort to the point of exhaustion; especially physical effort