punishing (adj.)
- arduous
- backbreaking
- burdensome
- corrective
- crushing
- demanding
- disciplinary
- draining
- effortful
- exhausting
- forced
- grueling
- hard
- hard-fought
- heavy
- hefty
- killing
- labored
- laborious
- onerous
- operose
- oppressive
- painful
- penal
- punitive
- punitory
- retributive
- strained
- straining
- strenuous
- stressful
- taxing
- tiresome
- tiring
- toilsome
- torturous
- tough
- troublesome
- trying
- uphill
- wearing
- wearisome
- wearying
