
So Leon….Quite a controversial character, to say the least. Some love him for being the undefeated champion with a Charizard, and many hate him for being the undefeated champion with a Charizard.
But the thing is, nobody can deny that at least lorewise, Leon is one of the best in the entire franchise. Being undefeated for more than at least ten years and winning one of the toughest leagues in his first try is truly a feat worth singing praises of.
Leon's presence in the entire anime is something that can never be ignored. Journeys clearly shows how much impact Leon has in the world of Pokémon battling with how hard people like Ash, Alain, Raihan, and Bea train in order to beat him and surpass him. How much he is respected among his fellow champions Diantha, Cynthia, Lance, and Steven for his incredible skills and strength. He is like the Gold.D.Roger of Pokémon. A man with influence on the world of battling so mighty that every other trainer wants to be like him.
Leon is, however, also known to be the one whom Ash faced in the greatest tournament of the world, Masters Eight, in order to become the very best of the world. Leon was his final obstacle between Ash and the title of World Champion. However, in my opinion, the battle was deeper than people seemed to realise. Let me tell you why I believe Leon might have been the perfect final obstacle for Ash.

First of all, what people don't realise is that Leon is basically just an older Ash with the similarities they have.
Leon and Ash are both trainers who started their journey from the countryside, starting respectively from Postwick and Pallet Town. Both of them hold a great love and passion for Pokémons and Pokémon Battles, as we see in episode 100, where Ash quote on quote, “trained” with Leon. The episode also showed us that just like Ash, Leon too is willing to risk his life in order to save others around him when he decided to take Eternatus head-on. Both of them also have an awful sense of direction too….Lol.
And the parallels don't end just there. Those who have read the Pokémon Adventures Sword and Shield chapters, they will be aware of the fact that Sonia stated that Leon is someone who keeps his problems to himself and doesn't like to show his vulnerable side to others. That's very similar to Ash, as he too prefers to be alone whenever he feels down, burdened, or troubled. Prime examples are his first six-on-six battle against Paul and his battle against Wulfric in Snowbell.
Leon also shows lots of care for his friends, just like Ash. They are also masters of adaptability, and both of them are always willing to learn from others [at least any Ash after Battle Frontier]. Ash learned the spin dodged from Dawn and got his inspiration for Counter Shield from Dawn and Leon did the same when he countered Ash's Gengar’s abilities to hide itself in the shadows, by using his own variant of Counter Shield.
However, it's not all just similarities. Leon also has many qualities that make him completely opposite to Ash, which makes him such a great final obstacle.
Ash was never a talented trainer. Like it or not, that's the truth. He was a good for nothing, talentless trainer who had no idea what to do and no proper guidance. Yeah, Brock and Misty did help him in many ways, but that was just mostly teaching him the basics of being a Pokémon Trainer. He didn't have what could be considered as a “proper” mentor. Ash was never meant to be a genius, he was never meant to be a talented or successful trainer. Literally the first episodes of the first season is filled with people belittling Ash for his lack of talent and skills alongside his lack of knowledge on Pokémon. That's what it was all about. Ash is someone who was meant to rise to the top solely on his hard work and prove to everyone that anybody can be anything they desire if they work hard enough.
