I have some faceoffs, here we go....
1. African hunting dog vs Arabian wolf
2. Leopard vs Gray wolf
3. Brown Hyena vs Chacma baboon
4. Mountain gorilla vs cougar
5. Wolverine vs Iberian lynx
6. African buffalo vs kodiac bear
7. Yak vs American bison
8. Blacked backed jackal vs Rhesus macaque
9. Siberian tiger vs Kamchatka brown bear
10. Rhesus macaque vs coyote
11. Asiatic black bear vs warthog
12. Spotted hyena vs sun bear
13. bobcat vs ratel
14. Tiger shark vs walrus
15: Main event: Great whie shark vs walrus
1. African hunting dog vs Arabian wolf: The African hunting dog will weigh about 50% more than the Arabian wolf. These animals have similar attributes (lateral quickness & mobility, jaws, endurance), but the African hunting dog is well-practiced at dealing with other predators & large prey items to a higher degree. A parity battle would be close, but at these weights the wild dog will prevail. African hunting dog wins.
2. Leopard vs Gray wolf: The leopard can weigh about 50% more than the gray wolf, but even a parity fight would favor the leopard. Leopards are armed with a strong bite & four sets of sharp claws, and the gray wolf only has a strong bite. The grey wolf does have an endurance advantage, but it will get overpowered quickly enough by the leopard to make it a moot point. The leopard's agility, quickness (especially with paw swipes), use of front paws for gripping & controlling, & finishing know-how (with a throat bite) will give it the ammunition to defeat the wolf. A leopard would be a tough matchup for 2 gray wolves. Leopard wins.
3. Brown Hyena vs Chacma baboon: A brown hyena can be 20-30% heavier than a chacma baboon. Brown hyenas have strong jaws with shearing teeth that can easily injure a baboon in a conflict. The baboon's mobility will enable it to land a few good bites of its own (with upper canines close to 2" long), but will have trouble mounting a counter-attack once the brown hyena latches onto it. The shaggy coat of the brown hyena will hold up better to the baboon's bite than the baboon's hide will hold up to the hyena's bite, but a few quick, well-placed bites from the primate could shift things into its favor. Its a dangerous fight for the brown hyena, but it should be able to prevail more times than not. Brown hyena wins.
4. Mountain gorilla vs Cougar: The gorilla will be about twice the cougar's weight. The cougar will have some advantages in this fight, including agility, quickness, use of paws & claws, & killing experience. However, a gorilla is brutally strong, and had grabbing hands & long, powerful arms than can help dictate the positioning of the battle or deliver blows to the felid's body. The bite of the gorilla is dangerous as well. The claws of the cougar can certainly cause significant damage to the gorilla's hide, but the overall offense of the much larger ape will usually be enough to deter the cat more times than not. Edge to mountain gorilla.
5. Wolverine vs Iberian lynx: These animals will be close in weight. Wolverines are among the strongest mammals pound-for-pound, and have jaws capable of crunching through frozen meat & bone. Wolverines also have stocky limbs with sharp claws & thick fur that can help buffer against a lynx's attack. Lynxes are quick & agile, but will have a hard time clawing & biting effectively against the robust wolverine while dealing with the mustelid's attack. A lynx would need a decent size advantage to deal with a wolverine. Wolverine wins.
6. African buffalo vs Kodiak bear: These animals will be close in weight, and the bear's shoulder height will be almost 90% of the buffalo's. A large, mobile buffalo can present problems for a bear because the bear won't have the lateral quickness to avoid many of the bovid's charges. However, bears are durable enough to withstand attacks most animals can't, and have great endurance to aid them in a prolonged battle. The Kodiak bear can stun the buffalo with powerful paw swipes, but it's best strategy (in order to avoid the horns) will be to grab the front end of the bovid with its forepaws to immobilize its offense. If the bear can hang on until the buffalo tires, it will be able to pull it to the ground & finish it. Close fight at parity, but the more diversified offense of the bear should enable it to win more times than not. An African buffalo weighing 20-25% more than the bear would likely be more than a match for it, but an equal-weight battle favors the bear. Slight edge to Kodiak bear.
7. Yak vs American bison: These animals are close in weight, but the bison is a more formidable animal. Yaks are generally docile, and don't have the same "mean streak" many other bovids do. Bisons fight by ramming with their heads & hooking with their horns, and would overwhelm a yak on most occasions. Yaks can be dangerous if forced to defend themselves, but they aren't on the same level as a bison. American bison wins.
8. Blacked-backed jackal vs Rhesus macaque: The black-backed jackal will weigh almost 50% more than the rhesus macaque. Black-backed jackals can feisty & confrontational, and use their jaws in a conflict. The rhesus macaque has mobility, use of hands, & sharp teeth that will aid it in a confrontation, but will have some trouble against a larger jackal. Probably close to 50/50.
9. Siberian tiger vs Kamchatka brown bear: The Kamchatka brown bear will weigh close to twice the Siberian tiger's weight. Tigers are capable of subduing animals larger than themselves (typically herbivores), but a brown bear presents many problems. Bears are not as quick or agile as tigers, but still have the ability to counter-attack one that engages it. The larger bear will have a hefty strength advantage, and its forelimbs can be used to dictate the positioning of the battle. A paw swipe from this bear can easily injure the tiger, and the ursid's superior endurance will give it a decisive edge in any prolonged encounter. A tiger would have a decent chance if the weights were reasonably close, but the felid will have it's work cut out for it against a brown bear of this size. Kamchatka brown bear wins.
10. Rhesus macaque vs Coyote: The coyote can weigh 3 times as much as a rhesus macaque. The rhesus macaque has mobility, use of hands, & sharp teeth that will aid it in a conflict, but it's giving up too much size here. The bite of the coyote will be too much for the monkey to deal with. Coyote wins.
11. Asiatic black bear vs Warthog: The Asiatic black bear will weigh over 30% more than the warthog. Asiatic black bears primarily eat fruit, nuts, leaves, & insects. They aren't on the same level as a brown bear in regards to combat, but they're still quite capable. Warthogs are nimble herbivores armed with long tusks, and can be dangerous to any attacker. The Asiatic black bear doesn't tackle large animals in its habitat, and would likely be driven away by an angry warthog in a realistic confrontation. However, if the bear is determined to fight, it has the assets (grabbing paws, claws, strength, endurance, jaws) to be favored against the smaller warthog (but a parity battle would be about even). Edge to Asiatic black bear.
12. Spotted hyena vs Sun bear: These animals will be close in weight. Spotted hyenas have bone-crushing jaws & great durability. Sun bears have sharp claws & loose skin that enables them to effectively counter-attack even when grabbed in an attacker's jaws. Even if the hyena latched onto the bear, it would likely be in a position to inflict damage to the hyena with its claws. A sun bear would be able to repel a spotted hyena on most occasions in a realistic confrontation, and would be slightly favored in a serious fight. Edge to sun bear.
13. Bobcat vs Ratel: The bobcat will be slightly heavier than the ratel (honey badger). Ratels have strong claws (great for digging), powerful jaws, and very durable hide that protects it from many attacks. The bobcat will have an advantage in speed & agility, but it will not cause as much damage to the ratel with its claws & bite as the ratel will cause to it. Much like the wolverine vs lynx contest, the bobcat will need a decent weight advantage to compete with the fearless ratel. Ratel wins.
14. Tiger shark vs Walrus: The walrus will weigh almost 3 times as much as the tiger shark. The walrus has very tough hide & is armed with long tusks (3') that can injure or kill adversaries with a well-placed stab. The tiger shark has jaws armed with razor-sharp teeth that are capable of penetrating the hide of the walrus. The walrus has better overall mobility in the water than the shark does, but can't duplicate the shark's bursts of speed. This battle will depend on whether or not the tiger shark can inflict enough serious wounds to the walrus before it gets impaled by the pinniped's tusks. Sharks are ambush predators, and aren't especially good as face-to-face combatants. Edge to the walrus.
15: Main event: Great white shark vs Walrus: The great white shark will weigh about 25% more than the walrus. The walrus will have greater overall mobility in the water, but won't be able to make the same quick movements of the shark. The hide of the walrus is extremely tough (polar bears have a hard time breaching it), and it covers a thick layer of blubber. However, the razor-sharp teeth of the great white shark can slice into a walrus & induce blood loss rather easily. The tusks of the walrus can kill the shark with a precise strike, but the chances are great that the shark will land a significant bite before that happens. Great white shark wins.