Synonyms and related words :
arduous, burdensome, crippling, debilitating, devitalizing, difficult, draining, enervating, enfeebling, fatiguesome, fatiguing, grinding, grueling, hard, harsh, heavy, killing, laborious, onerous, oppressive, overburdensome, punishing, sapping, straining, strenuous, stressful, tiresome, tiring, toilsome, trying, tyrannous, weakening, weariful, wearing, wearisome, wearying, weighty