Synonyms and related words :
Herculean, abstruse, arduous, assiduous, backbreaking, brutal, burdensome, complex, critical, crushing, delicate, demanding, difficile, difficult, diligent, effortful, elaborate, exacting, forced, formidable, grueling, hairy, hard, hard-earned, hard-fought, heavy, hefty, industrious, intricate, jawbreaking, killing, knotted, knotty, labored, laborious, mean, no picnic, not easy, onerous, oppressive, painful, painstaking, punishing, rigorous, rough, rugged, sedulous, set with thorns, severe, spiny, steep, strained, strenuous, thorny, thorough, thoroughgoing, ticklish, toilsome, tough, tricky, troublesome, uphill, wearisome, wicked