Fatal Flaw / Pokémon

• Ash Ketchum, the series lead for 26 years, had two that were holding him back.
  • His biggest flaw in the series was his immaturity. Despite loving Pokémon so much, his insecurities about whether or not he had what it took led him to develop an ego the size of a Wailord, promptly turning him into a reckless, lazy, haughty young man who thought he could take on the entire Pokémon League and win because he was Ash Ketchum. Predictably, he barely scraped his way by during his Kanto Journey, getting over half his badges out of pity and not skill and only making it to the Top 16 of the Indigo League through dumb luck. This devastating loss forces humility on him, and he starts taking things more seriously to eventually train his way up to more well-earned victories, higher league placements, and far more powerful Pokémon.
  • The next was his sole reliance on The Power of Friendship. True, it gained him some powerful Pokémon who grew on their own terms to become stronger alongside their trainer, but come Diamond and Pearl, this crutch is brutally exploited by Ash's rival in Sinnoh, Paul, who promptly wipes the floor with Ash using cold, calculated strategy that turns Ash's reliance on his Pokémon against him several times over. After a brutal 6-2 loss to Paul at Lake Acuity, Ash finally realizes he has to apply actual strategy to his matches in addition to friendship, which helps earn him a narrow win over Paul at the Sinnoh League and allows him to keep growing from there.
• Misty's is her temper. Although she was somewhat more mature than Ash and actually had proper experience from being a Gym Leader, she demonstrated that if she flew off the handle (and it didn't take much to set her off), she could be just as stubborn, immature, and hotheaded as he could be. When she finally did mellow out after she started being nicer to Ash (thanks to being Promoted to Parent to care for a freshly-hatched Togepi), she started honing her skills as a Gym Leader and managed to finally grow stronger.
• Brock's is Casanova Wannabe tendencies. Though a skilled Gym Leader and an expert Breeder, he drops everything he's doing and tries to flirt with every pretty woman he sees, especially Officer Jenny and Nurse Joy (whom he can tell apart down to the smallest detail). It's funny for the audience to see him suffer such misfortunes, but all of this proves to be little more than a distraction to his obtaining his goals; even when he does settle down on becoming a Pokémon Doctor and leaves Ash's group to study for it, he throws away his prospective career he just obtained to run a restaurant with yet another pretty girl he just met...that he didn't even bother checking to see if she was single first!. Makes one wonder if Croagunk's constant Poison Jabs in the rear was his way of telling Brock to stop getting distracted and actually do something with his life...
• May's is her underconfidence. She has the talent to be a great Coordinator, but she's so worried about making mistakes or lacks such faith in her own abilities that she makes crucial mistakes along the way. Her battle against Drew in the Kanto Grand Festival nearly turns pear-shaped because she started losing confidence, and when she does lose to Solidad rather lopsidedly, the loss crushes her so badly that she spends the last of the Battle Frontier arc in a very bad funk over it, losing a practice round to Drew in the process. Part of the reason she leaves Ash's group for Johto is so she can find her way, which Journeys implies she does given how widely respected she is as "The Princess of Hoenn."
• Dawn's is perfectionism. Given that she's the daughter of the legendary Johanna, a world-renowned Top Coordinator, she's eager to follow in her mom's footsteps. Unfortunately, she's so overconfident and focused on fine-tuning her performance to perfection that she loses her first contest, and winds up failing to make the second stage twice in a row. Zoe and Wallace both point out to her that she'll only be able to get further if she loosens up and has fun with her Pokémon. Luckily she does, and things go better for her in the long run.
• Iris' is her immaturity. Despite all she frequently bags on about Ash "being a kid", she's still plenty green around the gills herself, and doesn't have the knowledge or experience to become a Dragon Master like she wants. Part of this stems from her inability to control her Pokémon due to a lack of understanding of them — her Axew is still just a baby, she pushed her Excadrill too hard during her last battle with it and lost all respect for not considering its feelings, Emolga is too much of a spoiled brat to reign in like she wants, and her Dragonite is too much of a Blood Knight to listen to her commands. She eventually takes the time to get to understand them better and they start listening to her, which Journeys shows made her Champion of Unova.
• Serena's growing crush on Ash is adorable and ironic, especially since it's one-sided on her part. Zig Zagged as her infatuation becomes a source of strength for her, as she starts her journey because she saw him on TV and wanted to reconnect with him after years of not seeing each other while also finding a dream to pursue for herself. However, during the XY series, she spends much of her time vying for his approval, which causes her to become stuck in a rut. She eventually realizes that she must chart her own path, even if she still desires Ash's love. When she leaves the group, she does so under the promise that Ash is her goal but intends to do so patiently.
• Lillie's is her own fear of Pokémon. She admits that she loves them and wants to know more about them, but she just can't bring herself to touch them despite this. She slowly works towards overcoming her fear but regresses back when it's revealed A Nihelego attacked her when she was little, but Faba buried her memories after Nebby the Cosmog accidentally brings her in contact with Type: Null. When she directly confronts those fears after facing both Faba and that same Nihelego, she manages to overcome her trauma and set off on a quest to find her missing father. In fact, by the end of Ash's tenure as the series lead, she's the only one of Ash's companions to accomplish her goals, having found her father and welcoming the Shiny Nihelego that saved him into the family.
• Goh's is his single-mindedness. Ever since he met Mew as a child, he's been focused on capturing Mew and Mew alone, isolating himself from everyone and having very few friends aside from Chloe. He does find a new friend in Ash when both are recruited as Research Fellows, and he does decide to start catching other Pokémon to better understand Mew, but his stubbornness and lack of understanding briefly cause his Raboot to turn against him for not bothering to teach it Ember, his Drizzile runs off when Goh fails to get why it's upset about not evolving into Inteleon, and his disliking of Gary's constant taunting during their Project: Mew missions together keeps him from working together with his rival properly. Even if he does make friends, he's so finicky about how he defines that friendship that he considers it a "betrayal" if they do something to his dislike; a boy he met named Horace failed to meet up with him to search for Celebi, which Goh took personally until he learned Horace got sick that day, and at the end of the series, declares his friendship with Ash over when Ash decides to go on a journey alone, despite Goh wanting to do the same (though luckily Lugia stops by and fixes things).
• Chloe Cerise's is her indecisiveness. Her father is a famous researcher, and everyone's pressuring her to do the same, but she's not sure what she wants to do with her life at all. Meeting an Eevee that somehow can't evolve results in her starting to take up research to see what this Eevee might want to evolve into, but the multitude of choices makes it hard for either party to decide. She settles on keeping Eevee as is for now, and grows fascinated by the subject of Pokémon Evolution enough that she takes up a Research Position when Ash and Goh leave.