Sixth Ranger Traitors in Anime and Manga.
- In Attack on Titan, Floch Forester is a late arrival to the cast, having been a classmate of the main characters that did not enlist in the Survey Corps. He has a change of heart and decides to switch branches to begin working with his old classmates and seems to be a Red Shirt in the making. Instead, he's the Sole Survivor of the suicide charge against the Beast Titan. After the Time Skip, he quickly establishes himself as a Token Evil Teammate that clashes with Jean over ethics and eventually betrays the Survey Corps entirely as The Dragon to Eren's radical Yeager Faction.
- Corrector Yui - One of Yui's closest friends was the true Chosen One to be the titular Corrector, but I.R. chose Yui because of an error, which was later elaborated as she was infected by Grosser at the time. It's Haruna, and no, its not "a hidden grudge" it was pure Mind Control -as it was later the case with Shun- before being recruited after Inukai told everyone in the group about it; then after she tried to leave the group (because Yui was better for the Correctors), Grosser takes her and turns her against Yui. Haruna is eventually cured by Yui herself in an "I Know You're in There Somewhere" Fight, goes under temporal retirement (she was still remaining as Mission Control) and, in the second season, she rejoins the team as Sixth Ranger.
- In Death Note, Light Yagami joins the secret police taskforce in charge of finding and stopping Kira, a brilliant but crazy serial killer who's using an Artifact of Doom to anonymously murder anyone he deems evil, which can reach triple digits on a single day. Unfortunately, Light is Kira.
- It's played with, in that L, the leader of the task force, is never in any doubt that Light is Kira - inviting him to join the task force is just a ploy to attempt to prove his guilt. It works. Eventually. Not that L's around to see it.
- In Digimon Universe: App Monsters, the Applidrivers gain a Sixth Ranger in the form of Yuujin Oozora, Haru's best friend, and his Buddy Appmon Offmon mid-series. Rei finds the new addition to the team too eager to help and friendly, but the other Applidrivers and their Buddy Appmon see this as a bonus and welcome their new teammates with open arms. In the climax of the series, the horrible truth is revealed: Yuujin is actually YJ-14, an Artificial Human created by Leviathan to keep tabs on Haru and collect data on humans by living among them. Even his own Buddy Appmon didn't know this! This is obviously devastating to the Applidrivers, especially Haru. However, being Haru's friend for half a decade made Yuujin grow a heart and personality of his own, so Leviathan has to take total control of his body to make him fight against his loved ones. When he regains control of his body, Yuujin is heartbroken over Leviathan's actions, and ends up making the choice to delete Leviathan at the cost of his own life, partially to prevent Haru from making that awful choice himself and living with having killed his best friend for the rest of his life.
- Genpou Saji from Ikki Tousen starts like this, manipulating both Rakuyou and Nanyou as The Man Behind the Man. After being defeated, though, he becomes a genuine Sixth Ranger. In the anime, at least. The manga's a bit more involved, but Saji was never evil.
- Team Trinity in Season 1 of Mobile Suit Gundam 00. They appear out of nowhere to rescue the Gundam Meisters of Celestial Being, but once meeting them in person, they act secretive and hostile towards them. They go along with the idea that they both want to eliminate war by force... or at least, that's what Johann believes. His siblings, Michael and Nena, are sociopaths who care little to none about their job, and their later antics end up making Celestial Being as a whole look really bad. As a result, the whole world starts cracking down on them as a whole, and even manage to acquire technology to beat them back, proving that they are only as strong as their Thrones let them be. Still, they don't betray Celestial Being... Setsuna just decides they're causing more harm than good, so he attacks them, leading to both teams fighting against each other. It's ultimately revealed that Team Trinity was created by Celestial Being insider Ribbons Allmark, who intended them to smear Celestial Being's reputation so the world would unite against the Gundams. Once they served their purpose, Ribbons had no problem having them assassinated, despite the fact that they were pretty much his "children".
- Kaworu from Neon Genesis Evangelion, although there's enough visual and in-plots hints about people wondering about him that he was deliberately a mysterious character. His character showed up in one episode, which means the time from Introduction to The Reveal about his identity as The Last Angel was about fifteen minutes. Subsequent versions of the story reveal it even faster, likely because almost anyone watching a remake will know it anyway. Death & Rebirth reveals Kaworu's betrayal before introducing him! The fact that he's first seen in Rebuild of Evangelion hanging out with Keel Lorenz is a pretty big indication by itself that he's not on NERV's side in the latest iteration of the story, either. note
- There's also EVA-03 and its pilot; however, the case of their betrayal was unintentional, as an Angel managed to hijack them before they even made a sortie.
- Meowth of Team Rocket pretends to become a new ally for the heroes of Pokémon the Series: Black & White for one short Story Arc, but it was just to lure them into a trap in Nimbasa City.
- In the second season opening of Science Ninja Team Gatchaman, the team gets a new G-2 as a replacement for dead Lancer "Condor Joe" Asakura, much to the others' discomfiture. Surprise! He's a Galactor agent. Double surprise! Joe, Back from the Dead, kills him.
- A Downplayed example in Shaman King: while effectively leaving Yoh's team to join the X-Laws, Lyserg never fully betrays his companions and is still friendly and supportive of them, since they share a common enemy, and becomes a sort of Token Good Teammate to his new team. He eventually joins his friends back as one of the Five Elemental Warriors and leaves the X-Laws for good.
- Crona from Soul Eater is taken in after turning good, then is manipulated back to Medusa to be The Mole
- In the anime, Crona decides to stop working for Medusa and leave the DWMA out of guilt. Maka catches them on the way out and convinces Crona to stay and be their ally for the rest of the show.
- In the manga, Crona disappears just after being discovered, having been called back by Medusa to her lair. Eventually, Crona kills Medusa, but thought so lowly of themself for it that Crona decides to become a Kishin as Medusa planned and cause The End of the World as We Know It. Maka manages to talk Crona back, but by that point Crona had done so much wrong they ended up being a Barrier Maiden for the rest of their immortal life as repentance, or until Maka manages to rescue them, depending on your personal interpretation.
- Played with in Sword Art Online: After losing in a duel to Heathcliff, Kirito is forced to join the Knights of the Blood. After a costly boss raid with KoB, Kirito realizes Heathcliff is actually Akihiko Kayaba, creator of SAO and the one responsible for trapping all the players in the game. His ruse exposed, Kayaba reveals that he was setting himself up to betray the KoB and set himself up as the game's Final Boss.
