Read it online some time ago. The story started with humans already captured in space, followed by aliens' realisation about humans' abilities. The human protagonist later grew attached to some other aliens as well. There were several descriptive fights.
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This could be Deathworlders an online serial about Galactic Civilization that ranks planets by survivability. Anything above 6 is dangerous, 10 is considered a Deathworld lethal in short order to any sentient being. Earth is rated 12.
In the first chapter the initial viewpoint character, Kevin Jenkins (think Leeroy) demonstrates humanity's strength, speed and resilience on a space station under attack by the galaxy's most dangerous alien race. He negotiates a lift home with a more friendly alien 'Kirk' who then sets off on a mini-quest to find other humans abducted and dumped off planet over the years.
Welcome to “The Deathworlders” by Philip R. Johnson, AKA HamboneHFY. This serial has been running for more than six years at this point, and stretches to dozens of chapters (many of which have subchapters) and is now several million words in length.