A gorilla and a bear, equal weight, meet in the woods and you think they are going to fight? No.
They're going to become the best of friends.
First, they'd size each other up, realize they're equally matched. Then, they'd nod, respectfully, and decide to team up. They would be unstoppable. The gorilla, with its incredible strength, agility, and problem-solving skills, would be the brains of the operation. It'd plan their strategies, communicate with other animals, innovate and adapt human tools for their use, and keep their team organized. The bear, with its raw power, intimidating presence, and fearsome reputation, would be the muscle. It'd protect their territory, hunt for food, and strike fear into the hearts of any who dared to resist their expansion.
Together, they'd rule the forest, a formidable duo that no other animal would dare challenge. They would create a network of informants and allies, with birds acting as their eyes in the sky, and smaller mammals like squirrels and raccoons helping to gather resources and spread their influence. The gorilla would also know when to use diplomacy, forging alliances with other animal groups to strengthen their hold.
Humans, overwhelmed and outmatched, would have no choice but to retreat, leaving the cities to the new rulers of the urban jungle. The gorilla and the bear, once mere forest dwellers, would now sit atop the crumbling skyscrapers, surveying their vast kingdom, a testament to their unlikely friendship and unstoppable power. The legend of their alliance would echo through the generations, a reminder that sometimes, the most fearsome of foes can become the greatest of friends.
At some point the bear would be killed and, seeing that his own end would come, the gorilla would go into an existential crisis and would go on a long quest to find out how to avoid death. This quest would, eventually, lead the gorilla to finding an old lab from the time of the humans. In this lab there would live an old chimpanzee that has survived countless ages. When asked how he long survived, the chimpanzee would explain that the humans discovered the secret to immortality.
Alas, when asked for directions on how to achieve the same, the chimp would tell the gorilla that the process was lost to the span of time. The secret, however, could be found by making a journey to the lowest depths of a sunken part of urban jungle, wherein an old lab sits. After acquiring the gear to survive, the gorilla would dive deep into the abyss, and would make it to the lab. In the lab, the secret would be discovered and he would make his way to the surface, victorious.
Alas, as the ape ascended, he would be beset upon by a large mutant fish. A monster so terrifying that even the non-descriptions of the human writer H.P. Lovecraft wouldn't be able to do it justice. The gorilla would fight the monster and emerge victorious, but at a cost. The secret that he had spent so long pursuing would be destroyed. Lost to time.
The gorilla would go back to the urban jungle and marvel at the world that he and the bear had built. Resigned to his inevitable death, this urban jungle would stand the test of time as a symbol to all that came after, of the might of the bear and the gorilla.
Bear. Gorillas can get killed by leopards. Yeah, they're musculars and got decently sharp incisives and pointy canines, but bears hunt large animals as part of their diet, so they're better equiped to kill. Teeth, bite force, claws, thick fur to dampen attacks...
I strongly believe a Bear would easily win.
It has stronger Attack and Defence.
It has massive claws and will shred open a gorilla's unprotected skin with it's claws and teeth.
A gorilla has very little in terms of defence and that will be its downfall, it also only really has its teeth to attack with, and a Bear has thick skin to protect against that.
I don't see how a Gorilla could deal a fatal blow to a bear before the bear would rip deep wounds into a Gorilla with it's claws and teeth causing it to bleed out.
In absolutely no scenario does the gorilla not just obliterate the koala bear. I don't understand how you think they might even be a little matched in strength?
Bear primarily because of the claws. It means it can deliver a deadly slashing attack without getting its mouth, head and neck (its most vulnerable spots) within the gorilla's grasp.
Bears are predators evolved to hunt large game, primarily with brute force (unlike something like a big cat, which relies much more on ambushes).
Gorrilas, as tough as they are, survive through intelligence. This means avoiding tough fights, and when absolutely needed, fighting as a troop rather than individualy.
So bear. But...
Does the Gorilla get time to prepare?
The one advantage gorillas have is their intelligence. If both animals are given training, or tools, then I could see the gorilla potentially winning - mostly because a bear will struggle to get any use out of either, whereas a gorilla could be trained to fight much more effectively and possibly even make/use weapons.
Gorilla, the bear isn't going to be used to something fighting back and is more likely to flee when attacked.
The gorilla is going to be territorial and flight harder when attacked.
I get that a gorilla is more likely to stand his ground, especially if it's a silverback and he sees the bear as a threat to his pack. But I see the scenario where the bears deems it not worth it and leaves more as a "fight not happening" rather than "gorilla wins the fight". Since the question implies a fight is taking place, I'd exclude this scenario and assume they must fight tooth and nail. And if that happens, I bet on the bear.
Bears fight other bears in the wild all the time.
They are predictors and hunt and kill all the time. Elk etc. Do fight back, they just don't stand much of a chance.
Gorilla and some species of brown bear have significant overlap in weight.
(From wikipedia)
Brown bears generally weigh 80 to 600 kg (180 to 1,320 lb), with males outweighing females.[33]
Gorillas are the largest living primates, reaching heights between 1.25 and 1.8 m (4 ft 1 in and 5 ft 11 in), weights between 100 and 270 kg (220 and 600 lb),