Ash Ketchum has collected a total of 53 official Pokémon League badges over his time in the anime, including one he earned more than once. Some battles were surprisingly easy for him--Ash defeated the Hoenn region's Wattson without losing a single Pokémon, for example.
These battles, on the other hand, were a real struggle for him, with Ash either losing entirely on his first challenge or getting pushed to the brink before making a comeback. Here are 10 official gym battles where Ash really had to work to earn his badge--even if it took more than one attempt.
10 Roxie (Unova)
Roxie is a gym leader who was introduced in Black 2/White 2, specializing in Poison-type Pokémon. In those games, she's fought second, but Ash battled her last, meaning she pulled out a much more powerful team than she uses in the games. Roxie chose to battle Ash 3 versus 6, giving him the numbers advantage, and yet she still managed to knock out 5 of his Pokémon, with only a lucky paralysis from Pikachu saving it from total disaster. Most embarrassing for Ash is the fact that her first Pokémon was a Koffing, a Pokémon he should know well how to defeat due to Team Rocket by this point in the series.
9 Whitney (Johto)
Whitney is the third gym leader in Johto, and notoriously difficult to face in the games due to her Miltank. For once, Ash got a taste of what players of Gold and Silver had to deal with, as Whitney obliterated his Cyndaquil, Totodile, and even Ash's infamously powerful Pikachu on the first attempt with her Miltank's Rollout. Ash then foolishly chose the exact same team in his rematch, and nearly suffered the same fate before discovering a way to launch Miltank into the air and strike it while it was vulnerable.
8 Blaine (Kanto)
Ash's match against Blaine, the seventh gym leader of Kanto, is one that's very popular among fans, but it got off to a rocky start. Blaine's gym battlefield was in a volcano, making failure highly dangerous--Ash gave up on his first match when Pikachu nearly plummeted into the lava. In their rematch, Ash's Charizard was intrigued enough by Blaine's Magmar that it was willing to battle, and it subsequently proved its power by defeating Magmar with an epic Seismic Toss.
7 Roark (Sinnoh)
Ash's first Pokémon gym battle in a new region has a tendency to go poorly for him, and that was very much true in Sinnoh. Ash arrived to challenge Roark right as his new rival Paul won his own badge, and then invited him to watch. Ash then proceeded to get stomped by Roark's Cranidos, going through all three of his Pokémon to defeat it and embarrassing himself in front of Paul. Ash took a full episode to reconsider, but wound up having to face a Cranidos that had evolved the next time around. Turtwig emerged victorious after Ash deployed a unique strategy using burning leaves to conceal Turtwig's location.
6 Lt. Surge (Kanto)
Lt. Surge was the first gym leader Ash had to face that wasn't Misty or Brock. In fact, Misty and Brock were a little upset at Ash for going in so arrogantly, as they felt it made them look bad. On their first encounter, Lt. Surge's Raichu beat Pikachu so badly that Ash considered evolving it, only for Pikachu to reject the thunder stone and insist on fighting again as it was. Pikachu was able to take the rematch with a little clever strategy (using its tail as a ground for electricity) and its superior speed.
5 Wulfric (Kalos)
Ash's final gym battle in Kalos went so poorly that Ash actually wandered off into the woods afterward to reconsider his life and goals. The loss was brutal, as Ash never even made it to Wulfric's third Pokémon, and even his special Ash-Greninja wasn't able to pull out a win the first time around. Ash and Greninja spent an episode bonding and steeling their resolve for a rematch, where the new Ash-Greninja form reached full power for the first time, able to match up to Wulfric's Mega Abomasnow and secure victory (and a spot in the Pokémon League championship).
4 Brawly (Hoenn)
Ash initially looked down upon Brawly, as he saw Brawly out surfing rather than training, but he was in for a rude awakening when they actually battled it out. Fighting-type gym leader Brawly's Machop tanked a number of super-effective attacks before taking out Ash's Taillow, and his Makuhita evolved and easily defeated Ash's Treecko. Ash took a whopping 10 episodes before even attempting a rematch, spending much of that time training and preparing. Ash made clever use of his environment in the rematch, having Corphish attack from underwater and Treecko make use of its size to outmaneuver Hariyama.
3 Maylene (Sinnoh)
Another Fighting-type gym leader from Sinnoh, Paul battled Maylene first again and absolutely destroyed her confidence. It took a while before Maylene was even willing to accept Ash's challenge, and it at first seemed like an easy win for Ash, too. However, as Maylene got down to her final Pokémon, Lucario, she made a comeback, taking out Ash's Chimchar and Staravia with ease. It came down to Ash's Buizel versus Lucario, a battle between two Pokémon who love to fight which eventually ended in a tie. Maylene opted to give Ash a badge anyway, feeling he had proven his skill adequately.
2 Clair (Johto)
Ash's first battle with Clair, the last gym leader of Johto, was instantly memorable due to Charizard's timely return. However, Ash nearly lost his first match without even defeating her first Pokémon, until it was interrupted by a Team Rocket break-in. Charizard only joined Ash for the rematch, eager to battle against Clair's Dragon-type Pokémon. Her Kingdra was defeated by Ash's Snorlax, while Pikachu took care of Gyarados. That left Ash's Charizard to battle her Dragonair, which it defeated using a unique combo move that Ash called the "Flaming Seismic Toss."
1 Olympia (Kalos)
Ash's seventh badge in the Kalos region may have been one of his most noteworthy ever, as the gym leader Olympia had some powerful psychic abilities of her own which revealed to her an upcoming disaster. The battle was a rare double battle, with Olympia using two Meowstic that were trained to be in sync with each other, against Ash's Talonflame and Frogadier. Olympia had an actually pretty decent double battle strategy, using moves like Helping Hand that normally don't see much play in the anime. Frogadier struggled through much of the battle while paralyzed, making its performance even more impressive. Ash also had to keep track of the regularly predicted Future Sight attacks, giving him a lot to juggle at once. Still, he pulled out the win thanks to Frogadier's determination, setting him up for the upcoming Ash-Greninja reveal.
While Ash might not always be the most talented Pokémon trainer in any given room, he is almost always the most determined. It's this determination and drive that lead Pokémon's Ash to beating so many hard gym battles.