1) Arduous 2) Backbreaking 3) Chastising 4) Disciplining 5) Effortful 6) Fining 7) Grueling 8) Gruelling 9) Hard 10) Heavy 11) Imprisoning 12) Laborious 13) Like tough jobs 14) Penalizing 15) Putting a child in timeout 16) Resulting in punishment 17) Severe 18) Toilsome Found on https://www.crosswordclues.com/clue/punishing