Over the many years of Pokémon, Ash Ketchum has caught plenty of Pokémon, training them to "the very best, like no one ever was," but now, with the franchise over 20 years old, he's accumulated quite the roster to pull from. But of the many Pokémon he's trained -- which are the strongest?
Now obviously, the anime doesn't play by game rules, so simply comparing stats and type advantages is not an option. Likewise, we aren't looking for the strongest possible team that Ash could make, which would take into account type-advantages. Instead, we'll be following a few guidelines: one, Ash must have caught and trained the Pokémon himself; two, "strength" is determined by the battles they've won, and how well they've bonded and listened to Ash. Lastly, these are in no order in particular.
A Stubborn Sceptile Who Just Refuses to Lose
Ash's Sceptile was one of the few Pokémon he caught in the Hoenn region, and as result of being on such a small team, he got a lot of experience. While Sceptile did go through a rough patch during his evolutions, stubbornly doing his own thing, Ash was able to give the Pokémon the space he needed to work things out. As a result of this mutual trust, Sceptile became immensely loyal to Ash, eagerly and fiercely battling on his behalf.
Sceptile proved his strength definitively in Season 13, Sinnoh League Victors, Episode 32, "The Semi-Final Frontier," where it was the only Pokémon in the entire Lily of the Valley Conference to defeat Tobias' Darkrai, earning Ash a spot in the top four, and making him the spiritual runner up, as the actual runner up failed to K.O. the mythical Pokémon.
Naganadel Forges an Ultra-Close Bond With Ash
Naganadel may technically be an Ultra Beast, when it comes to the bond between trainer and trainee, in the Sun and Moon series, Naganadel's second only to the yellow mouse himself. One of the many Pokémon Ash befriended before officially catching, the space invader eagerly joined Ash's team of its own accord.
By playing, living and training together, Naganadel became strong, and while it did briefly return to Ultra Space, its love for Ash remained -- and it was this love (and a convenient wormhole) that allowed Naganadel to return and join Ash during the Alola league, making it instrumental in finally making Ash a Champion!
Greninja's Link With Ash Was More Than Metaphorical
While Naganadel's close bond with Ash was based around simply enjoying being together, Greninja's takes on a decidedly more shonen sense of nakama -- or allied friends. Not that Greninja didn't also adore his trainer, but that when it came to their interactions, Ash and Greninja were a little more focused on the battle than playing. From literally training together, to unlocking their Ash-Greninja form (the closest the Kalos Adventures got to letting Ash use Mega Evolution), these two were together against the world, and nothing could stand in their way.
Ash's Training Unlocked Infernape's Hidden Potential
One of the few Pokémon with a unique arc, we first meet Inferape as a Chimchar, under the "care" of Ash's rival Paul. When Chimchar's simply not strong enough for the callous trainer, it's released and then taken in by Ash. While Infernape definitely had some PTSD from its time with Paul, Ash's much more caring and fun-loving approach worked for the fire monkey, allowing it to evolve not just once, but twice!
It soon became a dependable partner, and under Ash's tutelage learned to control its Blaze ability, which had previously sent it into a rage. Thanks to this control, it was finally able to show Paul by defeating his Electivire that there is no such thing as an inherent set strength, but that, with kindness, patience and persistence, anyone can become strong.
Pikachu's Experience Makes Him Shockingly Formidable
No list like this would be complete without Pikachu. And indeed, the Mouse Pokémon is consistently one of Ash's strongest, with Ash having earned his trust a long time ago. The time the two have spent together and the memories they've shared have allowed Pikachu and Ash to understand each other completely, despite the language barrier.
Their innate understanding allows Ash to ask a lot of Pikachu, and Pikachu almost never fails to deliver -- whether that be with a brand new move Ash came up with on the spot or defeating yet another strong opponent. And, when it comes to pure power, Pikachu has mastered every attack it tried to learn, has an exclusive Z-move and even Gigantimaxed! Thanks to Ash's training and care, Pikachu has defeated everything from Route One birds to actual Legendaries.
Charizard Wasn't the Easiest To Train, But It Was Worth It
The only Pokémon besides Pikachu Ash has ever traveled with twice, Charizard's character arc is one of the most compelling in the series. While figuring out where his rebellious streak comes from is somewhat impossible, that very streak is what makes his bond with Ash so special -- because while Ash was trying to train him, Charizard was training Ash. His experiences with Charizard helped to form Ash into the kind, compassionate trainer we know today who doesn't mind when his Pokémon act up, instead of giving them the space they need to mature and grow.
As a result, Charizard is not only one of the most powerful Pokémon Ash has, having traveled with him through Kanto, Johto and Unova in addition to his personal training in the Charicific Valley, but has become one of Ash's most dependable. Whenever he's in a true pinch or really wants to go all-out, Charizard is the Pokémon Ash calls on. Add to this his potential for not one, but two different Mega Evolutions and Gigantimaxing in addition to Z-Moves using the crystals Ash obtained in Alola, and Charizard has to be one of the strongest Pokémon around.
