arduous vs punishing

arduous and punishing both are adjectives.

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

As adjectives, arduous and punishing are synonyms defined as:

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

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

arduous (adjective)	punishing (adjective)
difficult to accomplish; demanding considerable mental effort and skill	resulting in punishment
characterized by effort to the point of exhaustion; especially physical effort	characterized by effort to the point of exhaustion; especially physical effort
taxing to the utmost; testing powers of endurance