re: Biggest animal you could take in a fight

Any fast animal will close on you quick which renders the baseball bat almost useless except to block. You'll get about 1-2 swings before it gets in close.

With a baseball bat in hand, maybe a singular timber wolf or large canine. If they get the neck, you're done.

Other examples might be a walrus that you could keep your distance and use speed and the bat to your advantage.

A bear? No way, they'll crash right through that bat and throw your arse around like a toy.

Any big feline will kill you very quickly. Bat or no bat.