I always hated how in a lot of battle manga (Shonen and Seinen), the number of fighters for the final fight is usually the same. I get why it's done but it always annoys me so damn much.
Example being something like One Piece where almost every arc the final fight is between equal number of fighters on both sides.
I don't know why that's a problem, as long as the organisation doesn't have the exact same number of people as the portaginst it's fine,baroqworks did have more members but they got whittled down,even the cp9 has more members at the train.
I like it more like that, in the beginning there would be more people than the portaginsts then they get elimated throughout the arc untill they are equal.
And that's not true : punk hazard, whisky peak, wano(from the looks of it), whole cake island, sabody, impel down, marine Ford, amazon lily, thriller bark(the final fight was one opponent) , louge Town, zou, and jaya all didn't have one on one final fights the only ones so far: enemies lobby, dressrosa, alabasta, arlong Park, baratie, skypia (kind of) and fishmen Island.