exhausting (adj.)

• arduous
• burdensome
• crippling
• debilitating
• difficult
• draining
• enervating
• enfeebling
• grueling
• hard
• harsh
• heavy
• killing
• laborious
• onerous
• oppressive
• punishing
• straining
• strenuous
• stressful
• tiresome
• tiring
• toilsome
• trying
• tyrannous
• weakening
• wearing
• wearisome
• wearying
• weighty