Synonyms and related words :
Antaean, Atlantean, Briarean, Brobdingnagian, Cyclopean, Gargantuan, Homeric, abstruse, abysmal, arduous, astronomic, backbreaking, brutal, burdensome, colossal, complex, critical, crushing, delicate, demanding, difficile, difficult, effortful, elephantine, enormous, epic, exacting, forced, formidable, gargantuan, giant, giantlike, gigantic, grueling, hairy, hard, hard-earned, hard-fought, heavy, hefty, heroic, huge, immense, infinite, intricate, jawbreaking, jumbo, killing, knotted, knotty, labored, laborious, mammoth, mean, mighty, monster, monstrous, monumental, mountainous, no picnic, not easy, onerous, operose, oppressive, painful, prodigious, profound, punishing, rigorous, rough, rugged, set with thorns, severe, spiny, steep, strained, strenuous, stupendous, thorny, ticklish, titanic, toilsome, tough, towering, tremendous, tricky, troublesome, uphill, vast, wearisome, wicked