operose (adj.)

• abstruse
• arduous
• assiduous
• backbreaking
• brutal
• burdensome
• complex
• critical
• crushing
• delicate
• demanding
• difficult
• diligent
• effortful
• elaborate
• exacting
• forced
• formidable
• grueling
• hairy
• hard
• hard-fought
• heavy
• hefty
• industrious
• intricate
• killing
• knotted
• knotty
• labored
• laborious
• mean
• onerous
• oppressive
• painful
• painstaking
• punishing
• rigorous
• rough
• rugged
• sedulous
• severe
• spiny
• steep
• strained
• strenuous
• thorny
• thorough
• thoroughgoing
• ticklish
• toilsome
• tough
• tricky
• troublesome
• uphill
• wearisome
• wicked