There are any number of microbes I wouldn’t care to take on…
Technique would count for a lot. I’m sure that a human who had studied his animal opponents, learned their strengths and vulnerabilities and practiced methods of killing them, would be able to take down many more species than could a clueless jock. Even a dimwit would probably succeed against his 2nd or 3rd squirrel.
But it could work the other way, too. A squirrel could be trained to make a lightning fast leap and bite to the jugular and win the pot.