Therizinosaurus.

Of all animals that ever lived on earth, the Therizinosaurus probably had the longest claws. It used them to dig, grasp, pierce, and peel off bark. It lived towards the end of the dinosaur age, together with other herbivores such as the Kentrosaurus and Pentaceratops.

Fun fact: The claws of the Therizinosaurus were thought to be those of a giant tortoise when it was discovered.