Without the help of each one of these rivals, Ash never would have been able to achieve his long-term dream of becoming a Pokémon master.

The Pokémon anime’s longstanding protagonist Ash Ketchum has been declared world champion, finally achieving his lifelong goal of becoming a Pokémon Master. Given that it took over two decades for this to occur, it is well-known among fans that he couldn’t have done it without the help of his friends, family, Team Rocket to some extent, and of course, his own Pokémon. However, what really made him seek out challenges and risks — something he needed in order to become world champion — were the numerous battles he had with his rivals over the years.
Ash has had a plethora of rivals over the course of Pokémon. While some were very polite and friendly toward him, others were outright cruel and took time to gain respect for him. However, all of them had one thing in common: helping Ash improve his skills as a trainer, whether it was ethically, strategically, or both through their own methods. On the other hand, a select few have imparted a great deal more on Ash than others.
Gary Oak Instigated Ash’s Incredible Willpower

Being Ash’s first-ever rival in Pokémon, it is nearly impossible to forget Gary Oak. While he was undoubtedly a much better trainer than Ash, having somehow earned ten gym badges within a shorter time span, he was never afraid to try and get under the latter’s skin. This bullying occurred in multiple forms, whether it was flaunting his myriad of achievements in front of Ash or just laughing at him for careless mistakes, such as not waking up on time to receive his starter Pokémon.
In fact, it is well-known throughout the fanbase that Gary has a huge ego, complemented by his cocky and arrogant nature. While his actions have caused him to be heavily perceived as irritating, Ash used these encounters to encourage himself to never give up in hopes he could one day surpass Gary — which he actually does.
Paul Served as Ash’s Inverse in Pokémon

Much like Cobra Kai’s Johnny Lawrence, Paul believed one should approach battle without holding back or showing any mercy, making him one of the coldest trainers out there. Sadly, this abuse extended toward his own Pokémon — something Ash would never do. Contrary to Paul, Ash encouraged others to raise their Pokémon with love and patience, going so far as to take in one of the former’s as his own.
However, because Ash was so hung up on getting back at Paul for the way he treated others and his Pokémon, he suffered multiple losses against him, hindering his own career as a trainer. To combat this losing streak, Ash learned from Paul that he had to come to terms with the fact that not everyone was going to think the way he did, allowing himself to be more open to other battling styles while maintaining his own beliefs.
Gladion Reminded Ash to Be More Careful

Gladion played the role of Ash’s rival during his travels throughout Alola. Unlike his lukewarm counterpart in Pokémon Sun & Moon, Gladion is depicted as more compassionate and caring toward others while retaining his aloof and calm personality. While he has displayed kindness to Ash more than Gary or Paul ever have, the two of them still had their disputes. This includes an incident where Ash mistakenly reignites Lillie’s — Gladion’s sister — unease toward Pokémon, causing Gladion to brutally reprimand him in return.
However, if there was anything to take from this mishap, it’s that Ash learned even his friends would disagree with him at times. It reminded him to be more careful — not just with his Pokémon but his friends as well, showing he should not take them for granted.