Synonyms and related words :
adverse, antagonistic, conflicting, contrary, counter, counteractive, detrimental, difficult, draining, exhausting, fatiguesome, fatiguing, grueling, hard, harmful, hostile, in opposition, inimical, killing, miserable, not easy, opposed, opposing, opposite, punishing, rigorous, sinister, straining, tiresome, tiring, toilsome, troublesome, troublous, trying, unfavorable, untoward, weariful, wearing, wearisome, wearying, wretched