Onerous.
ADJECTIVE
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(of a task, duty, or responsibility) involving an amount of effort and difficulty that is oppressively burdensome:
"he found his duties increasingly onerous"
synonyms: burdensome · arduous · strenuous · difficult · hard ·
[more]
severe · heavy · back-breaking · oppressive · weighty · uphill · challenging · formidable · laborious · Herculean · exhausting · tiring · taxing · demanding · punishing · grueling · exacting · wearing · wearisome · fatiguing · toilsome
antonyms: effortless · easy-
law
involving heavy obligations:
"an onerous lease"
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