gruelling vs punishing

gruelling and punishing both are adjectives.

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

As adjectives, gruelling and punishing are synonyms defined as:

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

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

gruelling (adjective)	punishing (adjective)
characterized by effort to the point of exhaustion; especially physical effort	resulting in punishment
	characterized by effort to the point of exhaustion; especially physical effort