Punishing

Verb
punishing

Adjective

 * 1) That inflicts punishment
 * 2) arduous, gruelling

Thesaurus
Herculean, arduous, backbreaking, burdensome, castigatory, chastening, chastising, corrective, crushing, demanding, disciplinary, draining, effortful, exhausting, fatiguesome, fatiguing, forced, grueling, hard, hard-earned, hard-fought, heavy, hefty, inflictive, killing, labored, laborious, onerous, operose, oppressive, painful, penal, penological, punitive, punitory, retributive, strained, straining, strenuous, stressful, taxing, tiresome, tiring, toilsome, torturous, tough, troublesome, trying, uphill, weariful, wearing, wearisome, wearying