Synonyms and related words :
Herculean, abstruse, arduous, backbreaking, brutal, burdensome, complex, critical, crushing, delicate, demanding, difficile, difficult, draining, effortful, enervating, exacting, exhausting, fatiguesome, fatiguing, forced, formidable, grueling, hairy, hard, hard-earned, hard-fought, heavy, hefty, intricate, jawbreaking, killing, knotted, knotty, labored, laborious, mean, no picnic, not easy, onerous, operose, oppressive, painful, punishing, rigorous, rough, rugged, set with thorns, severe, spiny, steep, strained, straining, strenuous, stressful, thorny, ticklish, tiresome, tiring, tough, tricky, troublesome, trying, uphill, weariful, wearing, wearisome, wearying, wicked