With hundreds of Pokémon as well as having a metric crapton of characters, don't be surprised that there will always be a character that fans want to check on their cartridges and release them from their game.
Anime & Manga
- Tobias stands out amongst the hatedom of those who defeated Ash in the regions League for the sheer Diabolus ex Machina of using a Darkrai and Latios, without explanation how he caught a Mythical and Legendary Pokémon. While Ash's other League rivals got plenty of interaction and focus, Tobias only had a few mentions and cameos of buildup then disappears and hasn't been heard from since winning the League, meaning he never got the buildup or Rule of Cool that would make the character having such Pokémon feel legitimate and thus only existed as a Writer Cop Out. The Curb Stomp Cushion of Ash defeating Darkrai and Latios before losing when no-one in the region, even the other League finalist, was seen less as mitigating than that Ash should have won the League fair and square negating the inexperience Aesop justifying his prior losses. While the others who cost Ash the league have some defendersexplanation , Tobias has almost no defenders and is seen as the tipping point for the previously tolerable Ash's inability to win a League become perhaps the most widely reviled part of the series.
- Trip is the most consistently disliked of Ash's main rivals. He made a bad first impression after defeating a weakened Pikachu with his newly obtained Snivy, setting the stage for Ash's reset, and annoyed fans with his bland rival dynamic and unexplained classism against Kanto. Fans see him as an uninspired rehash of Gary and Paul, but without the charisma or psychological conflict that made them interesting. Not helping is how often he is subjected to The Worf Effect in the series' numerous Tournament Arcs, causing Ash to look even weaker in comparison due to his inability to beat Trip.
- Ash's Unfezant takes the crown as his most unpopular Pokemon. Not only is she extremely bland personality-wise, even by regional bird standards, but she was notoriously weak in battle, only getting one major win in the entire series while being nearly useless in almost every other battle. Possibly in response to this, she ended up getting unceremoniously written off before the series had even ended, sent to Professor Oak's lab ahead of time to make room for Charizard.
- The Mewtwo from Pokémon: Genesect and the Legend Awakened. It is quite unpopular with the fandom for filling a role that many believe could have been filled by the well-loved established Mewtwo character from Pokémon: The First Movie and its sequel, for having a voice and personality that contrast sharply with said original Mewtwo, for having no explanation as to how a second Mewtwo is even possible, and for generally being the Fleeting Demographic Rule personified. Even Miriam Pultro, its English voice actress and One of Us, knew that the role would be controversial. When Mewtwo returned for Super Smash Bros. and an episode of the Journeys series, they went with the original portrayal instead of this particular one, and this Mewtwo was Put on a Bus permanently with the release of Mewtwo Strikes BackEvolution, a remake of Mewtwo Strikes Back. After said movie was released, it was discovered that this Mewtwo was created due to rights issues surrounding the original Mewtwo rather than something more oblivious or insidious, and fans criticized the fact that this hadn't been explained in the first place.
- Scott from Emerald, due to his tendencies to appear or contact you at odd and inconvenient times.
- Mindy of Snowpoint City is hated for offering the player a Haunter for a Medicham while slapping an Everstone on said Haunter, making it incapable of evolving into a Gengar, a powerful, fan-favorite trade evolution, from said trade. Even her dialogue after the trade suggests that she's trolling you.
- The Spiky-Eared Pichu and the Pikachu-Colored Pichu in Pokémon HeartGold and SoulSilver. Not only does the former replace Celebi in an event, but there's pretty much nothing special about them except for their appearance and odd moveset. The Spiky-Eared Pichu can't evolve and can't be transferred to the fifth generation, meaning there's absolutely no reason to even bother with it. (The Pikachu-colored Pichu is at least a "shiny" Pokémon, which are normally rare in the games, though it is still considered a waste of an event as they are already technically accessible in-game, unlike most event Mons.)
- There's a girl riding a Stoutland throughout Heahea City who prevents you from visiting the Hano Grand Resort until Olivia is beaten because she wants to find every last hidden object in the city and the bridge connecting it to the resort, with her selfishness and role as a roadblock both contributing to her hate. By the time the resort becomes available, she'll be on the beach planning to look for even more items, not even apologizing for her hindrance earlier on. She still has the same role in Ultra Sun and Ultra Moon with the lone saving grace being that she doesn't appear in the resort itself anymore once it's unlocked.
- Sordward and Shielbert are heavily disliked for their hideous designs, Upper-Class Twit personalities, and being extremely disappointing and anti-climactic villains who only appear in the postgame before completely vanishing. In spite of their unpopularity, however, they do reappear in the Galar Star Tournament as potential teammates and opponents, and it is revealed that they funded the tournament as an apology for their actions in the postgame.
Gale of Darkness
- Michael's little sister Jovi. You're tasked with finding her at the beginning, she follows you around until you've collected the Machine Part, and insists you're her assistant the whole time. In general, she behaves as if you're an idiotic child that she has to babysit despite this being the exact opposite of the truth.
- From Pokémon Mystery Dungeon: Explorers, Chatot. He's a Know-Nothing Know-It-All, and the infamous Perfect Apples incident proved him to be a Horrible Judge of Character. To summarize Much of the rest of the team don't like his attitude much either, and even Wigglytuff won't hesitate to call Chatot boring. That being said, he's still a loyal member of the Guild and willing to take a hit for his team, and Explorers of Sky shows some of his Hidden Depths in one of the bonus episodes, but good luck finding anyone who's willing to defend Chatot's idiocy in this instance.
- Flower Crown Eevee was added to the Research Breakthrough as the only Pokémon in the roster during the two months leading up to Halloween 2019, leading to intense backlash on social media (and possibly becoming the most widely-panned Research Breakthrough reward to date). The intent behind the two-months-straight of Eevees, according to Word of God, was to allow players the chance to acquire Flower Crown variations of each Eeveelution- which is hard when there are exactly eight (including the as-of-yet-unreleased Sylveon) and three of those evolutions are tied to RNG without abusing the nickname trick.