>>42374093He isn't a character; he is a plot device. Basically the Champion has to exist as a quota for the games, and the entire point of the story is to surpass the Champion. Leon was made into Hop's brother to tie into his storyline. Leon also exists to bring you to Sonia, Magnolia, and Rose when the time is right. He even gives you the endorsement to compete in the league because the game is too lazy for the player to earn an endorsement from somebody with status. So Leon feels almost unnecessary at times, as his whole character's point is to boost other characters. Leon also fulfills the idiot genius trope, as he is somehow a gifted trainer despite being completely clueless at times.
As a Champion though, Leon uses some of the best Pokemon in the game, and it is clear the developers and director knew that Leon wasn't much of a character on his own so they compensated by buffing his team. He has Haxorus, one of the most powerful physical Dragon-types in the game; Dragapult, the game's late bloomer with two immunities; Aegislash, one of the most viable Pokemon in the game and was even nerfed for this game; the starter that is stronger than yours; a powerful third stage Pokemon whose typing complements his starter; and the Gigantamax Charizard with a strong and diverse movepool to compensate for its weaknesses. Leon probably ranks in the top 3 for the best Champion team. If his filler Pokemon were actually something better like another late bloomer, I'd rank him easily in the top.
Leon was shoehorned into the game too much and was far too abrasive as a character. Leon would have been better off as the type of character that only showed up at the end of the game, like Lance, and did not much else.