Interspecies Conflict/Who Wins?
Wildebeest vs Wild boar
Black rhino vs Gray Wolf Pack
Green Anaconda vs Cougar
Gorilla vs Spotted Hyena
Jaguar vs Black bear
Wildebeest vs Wild boar: A wildebeest can weigh over 600lb, which is a bit heavier than a large wild boar (typically doesn't exceed 440lb). Wildebeests are a common prey item on the plains of Africa, but they are no pushovers. Their curved horns and sharp hooves can be effective weapons, and they use these to defend themselves from lionesses, leopards, hyenas, and other predators. The wild boar is a difficult opponent for any attacker. It has very tough hide, sharp tusks, and the ability to charge and turn quickly. Wild boars are a targeted prey item in many regions across the world, but even formidable predators (tigers, leopards, wolves, etc.) proceed with caution when dealing with these dangerous suids. A wildebeest is a very fast runner, but the wild boar will likely have the edge in lateral quickness in a close-quarters contest. The wild boar will probably be able to employ its weapons with greater ease than the wildebeest will (will have easy access to the flanks and underbelly of the wildebeest), and its hide will be more resistant to injury than the antelope's will. Both can win, but the wild boar will be too tough on most occasions. Large wild boars in Russia can reportedly weigh more than a wildebeest can, and one of these giants would have little trouble defeating one. Realistically these 2 herbivores will be able to interact without any hostilities arising. Edge to wild boar.
Black rhino vs Gray Wolf Pack: A black rhino can weigh over 20 times as much as a large wolf and can stand almost twice as tall at the shoulder. A gray wolf pack typically doesn't exceed 10 members (including young) but can reach greater numbers on occasion. An adult black rhino is often too formidable for even a pride of lions to conquer, and large wolf packs often fail to overpower full-grown bison. A black rhinoceros is an aggressive animal with a tank-like build and extremely tough skin. It can make turns and charges with a lot of force, and its long nose horn (the longer of 2) can be a serious weapon to gore adversaries with. Regardless of how the gray wolf pack chooses to attack (bite % retreat; bite & hold at both ends while others attack), its assault won't have nearly the same effect as it will on a bison or a moose. It will be hard for the bites of the wolves to make much of an impact (especially with the rhino making movements to repel the wolves), and there's very little the wolves will be able to do to impede the movements of the much larger animal. Wolves will typically shy away from attacking dangerous animals if the lives of any pack members may be at risk (which is why wolves won't commonly attack healthy full-grown bison and moose). Grey wolves have very solid endurance and employ excellent teamwork when hunting or fighting, but the black rhinoceros is simply on a much higher level than any prey item a gray wolf pack ever encounters. A large male wolf can exceed 130lbs, but each member of the pack won't be this large. An average gray wolf weighs between 100-110lb (in some areas much less), so a wolf pack with 6 adults won't mean that there are 6 wolves each weighing 130lb. A massive wolf pack with many large males that attack with determination (and a lack of caution that isn't natural to the species) can certainly overcome a black rhinoceros over time, but no wolf pack will realistically make such an attempt. The wolves have good enough lateral quickness to avoid a lot of the black rhino's charges, but simply won't be able to make enough headway in an assault to make the action a fruitful endeavor. Check out my answers from 8/21/16 ("Wild Conflicts") for some interesting parallels (white rhino vs spotted hyena clan and hippo vs gray wolf pack). Black rhino wins.
Green Anaconda vs Cougar: A green anaconda can weigh almost twice as much as a cougar. Green anacondas are poor fighters on land (lack of decent endurance and mobility) despite being excellent ambush predators. The green anaconda has enough power in its coils to easily asphyxiate a mammal the size of a cougar, but the cougar's quickness, agility, and great reaction speed will make it hard for the snake to capture the large cat in a face-to-face encounter. The cougar has the weaponry (claws and teeth) to eventually overcome the boa if it's determined to do so, but the risk will be great enough to make it a bad idea for the cat to persist. The green anaconda isn't without hope, but these snakes won't do well on land against a large, mobile opponent without the benefit of ambush. The anaconda becomes much more formidable in the water. A cougar isn't a reptile-killing specialist like a jaguar is, and won't do well in water against a constrictor with a considerable weight and strength advantage. The green anaconda's stamina and maneuverability will improve dramatically in the water, and the snake will have a much better chance of achieving the position it wants in a battle with the cougar. Edge to cougar on land; edge to green anaconda in water.
Gorilla vs Spotted Hyena: A large gorilla can weigh almost 3 times as much as a spotted hyena. Gorillas have great strength, long arms with grabbing hands, and strong jaws armed with 2" canine teeth. Despite these attributes, the gorilla isn't an experienced fighter against animals of another species. Spotted hyenas typically hunt and fight in a group, and a single one won't be comfortable taking on a gorilla in a one-on-one battle. Spotted hyenas are extremely tough animals (many survive violent skirmishes with lions and leopards) with very impressive bite forces. They are somewhat clumsy in their movements when compared to wolves, but still have decent lateral mobility. In a hypothetical one-on-one encounter with a gorilla a spotted hyena will flee as soon as the ape begins its initial show of aggression, and any serious fight will lead to the hyena being physically overwhelmed by the much stronger animal. Even 2 spotted hyenas might not be able to succeed here. Gorilla wins.
Jaguar vs Black bear: Jaguars, the 3rd largest cats in the world, average about 200lb in weight and can reach 300lb on occasion. Some males in the Pantanal region of South America have reportedly reached 350lb. The American black bear can exceed 500lb, with some large males approaching 600lb. The smaller Asiatic black bear usually maxes out at 440lb. Jaguars are widely considered to be the strongest big cat pound-for-pound, and their bite force is greater for their size than any other big cat. Jaguars aren't as tall at the shoulder as cougars or leopards, but they are much stockier and more powerfully built. Bears have greater endurance than big cats, and although they won't battle with the same intensity as a big cat will at the beginning of a fight, they can battle strongly for a greater length of time. The jaguar will use its sharp claws to swipe and grip, and may attempt to land a killing bite on the bear with its large jaws. The black bear will swipe with its paws as well, and may use its forelimbs in as attempt to control positioning while it lands bites. Even the largest jaguar will have trouble against a full-sized American black bear because it will be giving up too much size and strength (check out my answer from "Interspecies conflict" from 1/25/14 regarding this matchup), but will have a decent chance against the Asiatic black bear (check out my answer from "None" on 11/2/13 regarding a jaguar vs an Asiatic black bear). A jaguar will have the edge over any black bear close to its weight range mainly because it is more practiced at killing animals in its weight range than the black bear is, but a large weight advantage by the bear will make the fight closer. Overall edge to black bear.