Pokémon Journeys is nothing if not a testament to Leon’s strength, almost more so than Ash’s (even after Ash defeated him in the Masters Eight Finals of the World Coronation Series). Leon spent his scattered appearances throughout Journeys windmill-dunking on the series' strongest trainers and getting lost the moment he left his yard. Heralded as Galar’s unbeatable Champion, Leon conquered the Galar League on his first try, completing the Gym Challenge and winning the Champion Cup in a string of battles that weren’t even close. In spite of Leon's bold claims that he has never been beaten, a flashback during his battle with Ash revealed that the young trainer is not the first person to have defeated him.
The winner of what appeared to be the inaugural World Coronation Series, Leon was almost annoying because of how foolish he made his opponents look, be they Gym Leaders, Elite Four or other Champions. His achievements extend even further, having once invited 100 powerful trainers from around the world to challenge him and beat them all. Ash remains the only person who’s ever even defeated more than two of Leon’s Pokémon in a single battle. Leon's first battle against Sonia, however, proved to be an entirely different test.
Leon Lost His First-Ever Battle
As Leon prepared for his Finals match against Ash, he found himself thinking back to the very first battle he ever had as a child. In this battle, Leon sent out his Charmander to battle Sonia’s Rookidee. Unsure of why he was suddenly thinking of that battle, Leon went out to battle Ash and took control of the match, despite spending most of it at a numbers disadvantage. It was only in the fourth and final episode of this battle, after he’d lost to Ash, that it was revealed that Leon lost that battle to Sonia.
While not saying out loud to Ash that he lost, Leon did admit that this battle taught him what Pokémon battles were all about. It’s not a huge deal that Leon once lost a quick battle between children and small Pokémon, but it’s an interesting omission from someone who has openly talked about how he’s never lost before. Perhaps it was the tears of frustration from that battle that made Leon so obsessed with winning that he was an adult, a Champion and officially the greatest trainer in the world before he lost again.
Ash's Loss Is Vital to Leon's Character Arc
Between that battle with Sonia and his battle with Ash, it seems that Leon never experienced a challenging battle again. He went training after beating Flint of the Sinnoh Elite Four because he and his Charizard hadn’t gotten to go all-out. He needed only three Pokémon to defeat Diantha, the Kalos Champion, in a 6v6 battle. Leon’s strength in battle was so overwhelming that it made his battles uninteresting. Leon is a Champion just like Lance, Steven, Cynthia, Iris, Diantha and Ash, and the rest of his peers -- some of the most interesting and popular characters in the franchise. That Leon should be their equal in title and superior in strength but uninteresting due to his unbeatable talent was not a good thing for his character or the series.
Galar’s unbeatable Champion isn’t a compelling character because he has no challenges to overcome. Leon, who was so shaken by his first loss that he went years without losing again, yet handled it with grace when he did, is much more interesting. Leon’s legacy as unbeatable came crashing down at the hands of Ash Ketchum and was tremendous for both of them, as Leon now has a new motivation to keep improving, while Ash has finally had his talent for battling unequivocally validated. While it’s odd that Leon would be outright dishonest about having lost before, it was still highly satisfying to watch him lose to Ash.