This is actually a pretty even battle, but I chose Therizinosaurus because hunts are unsucessful more often than not.

KaijuNerd is right, as modern predator success rates are 30-40% on average with some exceptions and I imagine it was the same for back then too. But I will say the Theri claws were brittle and unfit for combat so it'd have to just throw its weight around for a fight.

I don't know about you, but those claws would surely increase intimidation

That is true. Intimidation is more than half of animal fights. but if these two were forced into conflict like with roman colosseums did, Theri has little going its way unless it has something like toxic meat (like koalas do).

Most predatory failed hunts end before they begin (ex. the prey escaping by noticing the predator, fleeing, or the predator deciding its not worth it). When carnivores don't give up or go for the kill in desperation they typically win or cause both to die of injury.

Regardless, tarbosaurus is more fit for fighting. I'd certaintly bet on it in a head to head battle.