In the world of Pokémon, few things are more certain than Ash releasing his partners. Typically, Ash releases a Pokémon that is too powerful because the show prefers that he stay in endless mediocrity for as long as possible. The list of Pokémon that Ash has released is almost as impressive as the list of Pokémon he still owns, which raises the question: Could an All-Star lineup of Ash's released Pokémon land him a Pokémon League victory?
In Ash's defense, it's always in the Pokémon's best interest when he lets them go, usually so that the Pokémon can return to its homeland. While some, like Charizard and Gliscor, have returned to him and now live in Professor Oak's lab, others have not been seen since Ash let them go. Let's take a look at the six Pokémon Ash has permanently released that would make the most formidable team.
The second Pokémon that Ash ever caught, Pidgeot spent most of its time in Ash's care as a Pidgeotto. As per usual with his Flying-types, Pidgeotto was predominantly used for Team Rocket encounters as well as search and rescue operations. A Pokémon of average strength, it was nonetheless a staple of Ash's teams during his Kanto campaign.
After the Kanto League, the gang encountered a group of Pidgey that were being terrorized by a Fearow. Pidgeotto finally evolved into a Pidgeot in battle against the wild Fearow, quickly and soundly defeating it with its newfound size, strength and speed. Ash decided to leave Pidgeot behind to protect the flock of Pidgey from further aggression from the Fearow. Awkwardly, Ash promised to return for it...and 20 years later has yet to do so.
Ash encountered Lapras during his journey through the Orange Islands, winning its trust despite its fear of humans. Lapras primarily served as the group's mode of transportation, ferrying them from island to island. But Lapras was still a strong battler, notably delivering the final blow to earn Ash his first Orange Island Gym Badge. Eventually, Ash fulfilled his promise to Lapras by reuniting it with its lost family, and though they briefly reunited in the Johto Region, Lapras has not been seen since.
Primeape has an odd, brief history with Ash as his shortest tenured Pokémon, only appearing in two episodes while under his ownership. Initially a mischievous Mankey, the wild Pokémon stole Ash's hat and then evolved into Primeape from sheer rage when James of Team Rocket kicked it. Thanks to Ash's iconic ineptitude as a trainer during his Kanto adventures, Primeape was too powerful for Ash to use in battle.
When Ash decided to enter the P1 Grand Prix with Primeape, he finally gained the Pokémon's respect after saving it from a dangerous fall. Freshly bonded, Primeape showed off its battle strength by going on to win the whole tournament. In the end, another trainer offered to keep Primeape and help it train, to which Ash obliged.
Pseudo-Legendary Pokémon, like Goodra, are so powerful that they are second only to actual Legendary Pokémon. As such, it's no surprise that Ash quickly released Goodra once it was fully evolved. The Dragon-type Pokémon won Ash his fifth Kalos Gym Badge with its incredible endurance and power. Shortly after, Ash returned Goodra to its home in the wetlands in a similar manner to Pidgeot's release, so that it could act as a guardian for weaker Pokémon.
Goodra returned to Ash once to help him battle in the Kalos League, although its performance gets a bad rep thanks to the misfortune of its matchups. It fought a Fairy-type Pokémon to a draw, a remarkable feat for a Dragon-type, and fell to another Pokémon that was spamming a One-Hit K.O. attack, Guillotine. Ash's Goodra returned to the wetlands once more after his Kalos League defeat.
Naganadel is another impressive capture of Ash's, considering it's an Ultra Beast, a type of extra-dimensional Pokémon with strength comparable to a Legendary's. Ash has an on and off-again relationship with Naganadel, as it goes back and forth between traveling with him and living with others of its kind in Ultra Space. He only battled with Naganadel once, in the Alola Championships against Kukui, where it defeated the professor's Lucario and managed to inflict decent damage to his Tapu Koko, a Legendary Pokemon. Naganadel currently resides in Ultra Space, having parted ways with Ash once again.
Ash's Greninja might be the most powerful Pokémon he has ever owned thanks to its special Battle Bond ability. As a young Froakie, this Pokemon was notorious for refusing to accept the trainers that chose it as their starter Pokémon. When it met Ash, it deemed him worthy and the two shared the closest bond Ash has ever had with a Pokémon that doesn't sit on his shoulder all day. Ash relied heavily on Greninja throughout his Kalos campaign.
Ash's Greninja possesses the unique ability to transform, similar to Mega Evolution, thanks to its bond with Ash. This form, referred to as Ash-Greninja, is overwhelmingly powerful, as Greninja managed to land several strong hits on the Kalos Champion's Mega Gardevoir, which is no small feat. Greninja was eventually revealed to be able to see the roots of the giant monster that nearly destroyed the Kalos Region. To exterminate the remaining roots, Ash left Greninja in Kalos in his most heartfelt goodbye since Butterfree.
Could Ash's Released Pokémon Win a Pokemon League?
Considering these are some of the most powerful Pokémon that Ash has ever had, hence his releasing them, it surely seems feasible they would be enough to bring Ash his second League Championship. The team is well balanced, with speedy Pokémon that hit hard as well as bulky Pokémon that can take a hit. Along with Ash's creativity in battle, he would be a nightmare opponent with these Pokémon. It'd be very interesting to see what methods the series would employ to prevent him from ever winning with them.