backbreaking Synonyms

arduous heavy toilsome laborious grueling gruelling punishing hard operose severe sticky serious superincumbent rough taxing rugged strenuous thorny tiring effortful brain surgery laboured weighty walrus uphill trying troublesome tricky tough toilful profound ponderous plodding formidable exhausting exacting difficult demanding crushing complicated cloggy clayey ceramic burdensome grave grievous painful oppressive onerous leaden