Ash Ketchum has faced numerous different trainers over the course of his entire Pokémon journey, but it has not always been easy. He has faced several tough opponents that have either beaten him or taken him to his limits, giving him plenty to think about and work on as he continues his adventures.
The very beginning of his journey back in Kanto saw him struggling to get to grips with being a Pokémon Trainer, notching a mixed bag of wins, losses, and draws, as well as interrupted and unfinished bouts. He also fought with Team Rocket on an almost episodic basis, but with the lack of rules or discipline to their face-offs, they barely count as legitimate Pokémon battles.
10 Samurai Was Ash's First Real Opponent (Result: None Due To Interruption)
Ash Ketchum is on his way to Pewter City when he is challenged to his first official Pokémon battle by a Bug-type trainer named Samurai. Aside from encounters with wild Pokémon and Team Rocket, it is Ash's first challenge by a trainer which he excitedly accepts.
At this stage in the anime, Ash still knows very little about Pokémon, how to use them properly and how to work around type matchups. He calls on his tired Pidgeotto against Samurai and it is immediately defeated by Samurai's Pinsir. When Ash's Metapod defies expectations and nullifies Pinsir's offense with Harden, Samurai calls on his own Metapod for an intense standoff of very little movement or action. An approaching swarm of Beedrill interrupts the bout, meaning that no winner is determined.
9 Ash's Inexperience Was Exposed In Record Time By Brock (Result: Loss By Forfeit)
Ash's impatience is one of his worst character traits and it has worked to his detriment on numerous occasions over the course of the entire anime, but one of the first instances sees him challenge the Pewter City Gym Leader Brock before he is ready.
With Ash and Pikachu not yet being a cohesive unit, Ash encourages a terrified Pikachu to charge at the large and intimidating Onix with no real plan, almost instantly ending up in a deadly Bind attack by the hulking figure of Onix, forcing Ash to admit defeat.
8 Ash & Pikachu Were Able To Put Up More Of a Fight In The Rematch Against Brock (Result: Loss By Forfeit)
Following his humiliating defeat at the hands of Brock, Ash receives some help from the mysterious Flint, who helps Ash to prepare for the rematch by supercharging Pikachu, bolstering its power and stamina. Ash takes this newfound confidence into the rematch but instantly shows his inexperience by sending his disadvantaged Pidgeotto in for a quick defeat against the Rock type Geodude.
However, Pikachu's new power is then showcased with it defying the odds and Pokémon logic, defeating a part Ground type with an Electric type move. Pikachu appears to be on the verge of losing to Onix but the sympathetic Brock relents and tells Onix to stop, only for the sprinklers to be set off from Pikachu's previous attacks. This weakens Onix and allows Ash to capitalize, but he instead opts to forfeit, feeling bad about his fortuitous luck during the battle and vowing to win fair and square next time.
7 Misty & Ash Were Evenly Matched Before The Battle Was Stopped (Result: None Due To Interruption)
Ash is shocked to discover that Misty's reluctance to go with him to Cerulean City is because she is one of the sisters who take of the Cerulean Gym, but he challenges her regardless. Misty uses the water to her advantage, with Staryu using it effectively to counter anything that Butterfree throws its way before eventually knocking it into the water, forcing Ash to switch it out.
Despite this initial setback, Ash's Pidgeotto is on the verge of defeating Misty's Starmie when Team Rocket breaks into the Gym, interrupting the battle. This particular bout is never resolved, even if the two do face off multiple times later on in the anime.
6 Ash Recorded An Easy Win Against An Unnamed Trainer (Result: Win)
Ash Ketchum's first legitimate victory that is not against a wild Pokémon or Team Rocket comes at the start of "Path to the Pokémon League" when he breezes past an unnamed trainer by having his Pidgeotto defeat the opposing Rattata.
While the battle itself isn't important enough to show in its entirety, the aftermath showcases Ash's growing arrogance and overconfidence from obtaining two badges, with Brock and Misty watching on, knowing full well how he obtained those badges without completely earning them.
5 A.J. & His Powerful Sandshrew Were Too Much For A Desperate Ash (Result: Loss)
When Ash faces an ambitious trainer named A.J. who is chasing his 100th win without defeat, he is humiliated by losing both his Pidgeotto and Butterfree to a Sandshrew, despite the supposed type mismatch. Pikachu refuses to meet the same end as his friends, thus leaving Ash defeated and A.J. as the winner.
A.J. goes on to defeat Team Rocket as well and reach his goal of one hundred wins, and it is often considered a missed opportunity that he wasn't brought back as a proper rival for Ash somewhere down the line.
4 Giselle's Cubone Had Pikachu Beat With Its Aggressive Offense But Got Complacent (Result: Win)
In "School of Hard Knocks," Ash faces off against a formidable trainer named Giselle, with Pikachu going up against her Cubone. Pikachu has slow start and Ash grows increasingly frustrated at Cubone's use of its bone as a weapon. Ash has Pikachu change up its strategy, biting and clawing its way to victory when Electric-type moves prove to be ineffective.
Cubone is eventually hit by its own bone, making it upset, which Giselle deems to be the end of the battle and a loss for her. The battle may be a messy one, but it is still a big win for Ash as he starts to gain traction on his quest to become a Pokémon Master.
3 Lt. Surge's Raichu Humiliated Ash & Pikachu (Result: Loss)
By the time Ash arrives at his third Gym challenge against Vermillion City's Lt. Surge, he has amassed a full team offering a decent coverage of types. However, the battle against Surge is a one-on-one contest pitting Pikachu against its evolved form Raichu.
Raichu immediately brushes off Pikachu's Thunder Shock before unleashing its own devastating version of the move, leaving Pikachu seriously hurt. Pikachu tries to carry on but a Mega Punch, Mega Kick, and another Thunder Shock later and the battle is over, which is a devastating blow for Ash.
2 Pikachu Rallied & Exploited Raichu's Lack Of Speed In The Rematch (Result: Win)
Following his humiliating defeat to Lt. Surge, Ash turns to some soul searching as he debates whether to evolve Pikachu or not, with Pikachu deciding to stay as he is. After insisting on using Pikachu against Raichu once again, Brock informs Ash that Lt. Surge's early evolution of Raichu will have left it without the speed attacks needed to keep up with a quick opponent.
Pikachu takes some early attacks from Raichu but is quickly able to act on Brock's advice by running rings around his opponent, frustrating both Surge and Raichu to the point of desperation. From there, Pikachu causes Raichu to exhaust its electricity, leaving it vulnerable and ultimately defeated, earning Ash the Thunder Badge.
1 Ash Had The Gentleman's Raticate Beaten Before His Opponent Requested A Draw (Result: Draw)
By the time Ash and his friends reach the St. Anne, known as the S.S. Anne in the games, he has already amassed an impressive team on which to build on and train up. As they arrive on the ship, Ash immediately notices a Gentleman battling with a powerful Raticate, with it easily defeating an opposing Starmie.
Ash challenges the trainer to a battle, pitting his Butterfree against the impressive Raticate, but just as Butterfree appears to have the bout won, the Gentleman recalls Raticate and requests the match end as a draw, robbing Ash of a certain victory. The Gentleman then asks Ash to trade Butterfree for his Raticate, but despite Ash initially agreeing, he quickly goes back on his word and keeps Butterfree.