Back in East Blue, nothing was more intimidating than the fishman Arlong but in the grander scale of One Piece, Chopper could probably defeat him.

So he takes over a village to make it his base of operations and bleeds the people dry of their money and forces Nami into making maps and charts for one day rising up and taking over all the while paying off corrupt marines to not arrest him, this is where his plans start showing cracks; in the bigger picture, Fishmen are meant to represent the oppressed society, so when you do eventually learn about other fishmen and their struggles you become more sympathetic, all the while accepting that there are just flat out racists among said oppressed society such as Hody Jones, but you don't learn that until after the time skip, so when live action Arlong spells it out to you, the impact is kinda lost.
To play Devil's advocate if I did know about the fishmen's past going into Arlong Park, I would've thought someone of Arlong's strength could be a much bigger threat, instead he's a common pirate who couldn't hack it on his own and needs humans to do things that he should have no problem doing in the first place.