Although the largest subspecies of gorilla, the mountain gorilla, has incredible physical strength, a powerful bite and the use of hands, it would have little chance against a grizzly bear in a hypothetical confrontation. A grizzly weighs approximately twice as much as a gorilla and has great strength as well.
The grizzly bear's sharp claws are formidable weapons and would prove disastrous to a gorilla if they connected. In addition, the thick hide of a grizzly offers protection from attacks such as biting. A gorilla's best chance at surviving a hypothetical encounter with a grizzly bear would be to scare it off, as bears can be warded off by making loud, threatening noises.