How about a Ash who is just as OP as Paul Or Atem (Yu-g0-oh) ??
For example , Paul doesn't lose to anyone except The champion , A trainer with legendary Pokemon Or the Protagonist.
Same goes with Atem.
The
Pocket Monsters anime runs on themes of improving, getting stronger, and there always being someone better. None of this is possible to convey when your protagonist can only lose to the very top echelon of trainers.
Yu-Gi-Oh tells a different story. Atem was presented as special from the beginning, Satoshi was not. He's a regular, albeit talented, trainer who experiences struggles, who makes mistakes and who has to learn lessons. He has a relatable "everyman" element to him that Atem didn't, and was never meant to have.
While Satoshi should be good at battles (and, for the most part, he's presented as being so), I don't want to see a
Pocket Monsters anime where he can't lose to anyone who isn't a champion or doesn't have legendaries. That's boring. If anything, many of Satoshi's best character moments have come in the fallout of big losses. The fallout of his first Pokémon League, his loss to Touki, the big 6-2 loss to Shinji, etc. Because those are the moments when the character actually had to reassess the way he looked at a problem, change his way of thinking about it, and eventually came out stronger for it. This is what a protagonist like him is supposed to do.
Shinji, and I can't believe this has to be said again, wasn't the protagonist. He wasn't overpowered either, but that's a different discussion. Shinji had a different function in DP: Satoshi's primary antagonist. He only appeared sporadically and was built as being an especially tough trainer because otherwise it wouldn't mean anything when Satoshi eventually overcame him. And one of the reasons why the final battle between Satoshi and Shinji worked so well was because of the previous 187 episodes of Satoshi improving his battle style (ex. the Counter Shield), getting help from other experienced trainers (ex. the Air Battle Master, the COTD who helped teach Bouysel the Ice Punch move), and because of some of the bigger losses he'd taken over the course of his Sinnoh journey (note that Shinji brings up their earlier full battle after Satoshi calls in Bouysel).
The term "overpowered" isn't meant to be a compliment. If someone is referring to a character as "OP", it's usually as a part of a complaint that the plot has hurt the crucial element of drama by making a character too strong. Why would you want that to happen with Satoshi?