Grizzly bears - the ultimate carnivore:
Almost all queries received on this topic request answers to the lion versus tiger question. Oddly, few people simply ask which is considered the Ultimate Carnivore.
This honour is held by an animal the tiger does not often have encounter; it is the grizzly bear.
The grizzly bear is a poor predator, taking down a caribou only when the opportunity arises. This, however, shifted his evolution in favour of the job in hand, namely as a digger of hard barren ground for roots, tubers and den building. The grizzly bear subsequently evolved enormous bone and muscle density; roughly ten times our own for a given size. They have developed into huge and enormously powerful animals.
Big cat biology is very different. They have evolved powerful elastic muscles over a low weight, low density bone structure to suit their purpose of chasing down prey.
Grizzly bear pit fights:
The Californians of the late 19th century staged well-documented pit fights with grizzlies and spanish bulls. The grizzlies, using their paw as a club, shattered the unfortunate bull's skull or shoulder bones so easily that the betting became poor.
Eventually, and at considerable cost, African lions were brought in to raise the stakes. The most fierce of the adult males was sent in whilst the grizzly was already waiting in the pits. The lion was known for bravely charging straight in and looked good for the money, but the grizzly killed a male lion almost as easily as he'd killed the bull.