20 dudes with bats versus a single gorilla.
I feel like we are underestimating the SHEER QUANTITY of 20 adult men. Doesn't matter how old or fit they are when they have metal bats - those are strong enough to Hutt something and break something with an average full power swing.
The gorilla is strong, yes, but pain is still pain. It has a severe disadvantage in numbers - while he's trying to kill one man, another SEVENTEEN are going to be jumping him. The adult men are weaker, but have a full team.
Naturally, the adults are going to get more hits in, until they eventually circle around the gorilla and beat the living shit out of him.
The gorilla will naturally be able to take a few men out, yeah, humans aren't very durable. But if one man goes down, that means one man has two bats now. And it means every time the gorilla hits a man with tremendous strength to knock him out or kill him, it means another five men have an opening to ram their bats against his head, neck, and jaw.
The indomitable human spirit survives and conquers once more.