Cavendish (One Piece) possesses a dual personality, Hakuba, who is ruthless in slashing down everyone in range whenever Cavendish falls asleep.
Aoi Fukasaku (Coppelion) awakening her other personality, Izanami.
Aoi Kuchiba (The Qwaser of Stigmata) was cursed with her twin brother, Yū's personality when he accidentally killed him.
Utsuro (Gintama) developed countless multiple personalities to overcome the endless pain of immortality, one such is Yoshida Shoyo, though he ultimately killed the rest of them and resurfaced.
Yue's (Cardcaptor Sakura) false form, Yukito Tsukishiro, has his own identity and personality.
Mister Negative (Marvel Comics) possesses two personalities: the kindhearted philanthropist Martin Li, and the criminal mastermind, Mister Negative.
Unlike other Sonic continuities, this Super Sonic (Sonic the Comic) is the psychotic, murderous alter ego of Sonic the Hedgehog.
Celestialsapiens such as Alien X (Ben 10) all possess three distinct personalities who must agree on anything in a two-thirds majority vote for them to do anything.
Brigade (Marvel Nemesis: Rise of the Imperfects) constantly struggles with the minds of the one hundred Iraq War soldiers whose corpses make up his body.
Angel (Buffy the Vampire Slayer/Angel) often struggles with his murderous alter ego, Angelus.
Angel and Angelus (Buffy the Vampire Slayer/Angel) confront one another within Angel's mind.
Glorificus (Buffy the Vampire Slayer) shares a body with Ben, a human doctor.
Sakura Haruno's (Naruto) hidden thoughts are frequently expressed by her "Inner Sakura," who is at times shown to be a second personality.
Launch (Dragon Ball) constantly shifts between a kind-hearted, naive persona and a short-tempered, trigger-happy one whenever she sneezes.
The different aspects of Raven's (DC Comics) personality are represented by "Emoticlones" that reside within her mind.
Azrael (DC Comics) has a split personality that actually believes that it is the Biblical Angel of Vengeance.
Oozaru (Dragonball Evolution)
Goku (Dragonball Evolution) the human form/alter-ego of Oozaru.
Firestorm (DC Comics) possesses multiple minds and personalities via the "Firestorm Matrix."
Clark Kent (Smallville) has alternate personalities that surface when exposed to certain kinds of Kryptonite.
Kal (Smallville), Clark's personality that surfaces when exposed to red Kryptonite, represents Clark when he is free of his morals, inhibitions, and social conscience.
Kal-El (Smallville) is a persona of Clark's created when he was brainwashed by Jor-El, which struggled for dominance until Clark emerged victorious.
Nemesis (Resident Evil: Apocalypse) has two distinct personalities: Matt Addison, his former human self, and Nemesis.
Sailor Saturn (Sailor Moon) possesses both the souls of herself and Mistress Nine.
Moon Knight (Marvel Comics) has several split personalities, which also render him resistant to psychic powers.
The Prince of Persia (Prince of Persia: The Two Thrones) developed a second personality, the Dark Prince, when he was corrupted by the Sands of Time.
Coldstone (Gargoyles) possesses the souls and personalities of the three gargoyles whose remains compose his cybernetic body: Othello, Desdemona, and Iago.
Elisa and Ursula (Metal Gear Solid: Portable Ops) are split personalities who believe themselves to be the other's twin sister.
Mesogog (Power Rangers Dino Thunder)
Anton Mercer (Power Rangers Dino Thunder), the human alter ego of Mesogog.
Suikotsu (InuYasha) has two personalities: a kind, philanthropist doctor and a sadistic, murderous mercenary.
Dr. Jekyll (The Strange Case of Dr. Jekyll and Mr. Hyde) used a potion to manifest his evil impulses into a second personality, Mr. Hyde.
Niki Sanders (Heroes) sees her alter ego, Jessica in her reflection.
Gina (Heroes) is another one of Niki Sanders' alter egos.
After having the arm of Liquid Snake transplanted onto his body, Revolver Ocelot (Metal Gear) developed a split personality based on the deceased Liquid's thoughts, memories, and mannerisms, dubbed Liquid Ocelot.
Kalagua/Salupa/Dr. Eva Tabinas (Pedro Petuko) a great example of divided mind power.
The photo above is showing Josephine's (Anne Curtis-Smith's) Three inner goddess whom each have different powers and personalities.
Legion (Mass Effect) possesses the combined minds of over 1000 geth programs.
Moka Akashiya (Rosario + Vampire) has two different personalities; her original haughty one (Inner Moka), and an artificial one created from her mother's rosary (Outer Moka).
Harumi Chono (Paranoia Agent) has two very different personalities.
Maria (Paranoia Agent) a prostitute, Harumi's alternate ego.
Mike (Total Drama: Revenge of the Island) has multiple egos.
Chester a grumpy old man when Mike gets frustrated.
Svetlana the Russian Olympic queen of gymnastics when needed for athletic challenges
Vito a tough and aggressive Italian when Mike's shirt is off.
Manitoba Smith an Australian adventurer when Mike puts on a hat.
Mal is Mike's evil personality sealed within his mind who can shift between his and Mike's minds at his own will.
Spoony One and Dr. Insano (Spoony Experiment)
Cynthia Andrews (The Young Guardians)
Alfred Ashford (Resident Evil) developed a split personality based on his twin sister Alexia after going insane from loneliness.
Raiden (Metal Gear) has been overtaken by his "Jack the Ripper" persona.
Evil Ryu (Street Fighter), Ryu's persona when he has been overtaken by the Satsui no Hado
Kenshin Himura (Rurouni Kenshin) struggles with his alter ego Battousai the Manslayer...
...who's dominance of Kenshin's mind is signified by Kenshin's eyes turning golden.
After nearly becoming a Hollow himself, Ichigo Kurosaki (Bleach) nonetheless developed an "inner Hollow" alter ego.
Sensui (YuYu Hakusho) has 7 personalities, one counting his own and six others.
Alice (Bakugan) with her mask can take on her altered ego, Masquerade. Not only her looks and voice (and probably gender) has changed but Masquerade's personality is the complete opposite of Alice's.
Two-Face truly lives up to his name with having two sides of himself, one being a lawyer, the other being a killer.
Several different incarnations of the Hulk.
The Batman of Zur-En-Arrh (DC Comics) is a backup persona stored within Bruce Wayne's mind in the event he is overwhelmed by psychological trauma.
D.A.V.E. (The Batman) is a computer AI created from the combined brainwaves of several of Batman's enemies.
Every time Roger (American Dad) puts on a disguise, he develops multiple personas.
Touko Fukawa (Dangan Ronpa) mostly unwillingly switches to her murderous alternate personality, Genocider Syo, and back through fainting or sneezing.
Conner Kent (Smallville) has a unique reaction to red kryptonite, assuming the normally repressed genes and thought process of "Alexander Luthor".
Alexander Luthor (Smallville) is Conner Kent's darker personality brought out by red kryptonite.
Lex Luthor (Smallville), while stranded on an island, spoke with a man named Louis Leery, who he discovered was just a figment of his imagination.
Bad Cop/Good Cop (The LEGO Movie) has a Bad Cop Side
Good Cop/Bad Cop(The LEGO Movie) has a Good Cop Side
Kaede (Elfen Lied) possesses two distinct personalities: the murderous and sadistic "Lucy" and the childish and innocent "Nyu."
Two-Face (DC Comics) truly lives up to his name.
When to pass strict age limits, Penelope invented a disguise, giving herself under the alias, Black Baron, a pilot who wins the ACES Flying Competition each year.
The Black Knight (Sly Cooper: Thieves in Time) is another persona Penelope took under while working for Cyrille Le Paradox.
Hyde (Valkyrie Crusade) has a split personality.
Metalhead (Teenage Mutant Ninja Turtles; 1987 TV series)
Under the effects of the Joker infection and Scarecrow's fear toxin, Batman (Batman: Arkham Knight) developed a split personality based on the Joker.
Quincy Sharp (Batman: Arkham) has a murderous split personality that believes itself to be the spirit of Amadeus Arkham.
Noire (Fire Emblem Awakening) developed a more brash and violent split personality as a result of being used as a test subject for her mother Tharja's curses.
Zofis implanted a strong darkness inside Koko’s (Zatch Bell!) heart in order to make an ideal partner. By infusing the darkness with Koko’s hidden pain and jealousy, Zofis created a separate personality who enjoyed hurting others as much as he did. Zofis used this evil Koko as a partner while keeping her true, kindhearted side locked away.
Kolulu (Zatch Bell!) has a separate personality inside her spellbook. Whenever Kolulu’s bookkeeper Lori reads the spell Zeruku Kolulu’s sadistic side is released.
Diana (Marchen Awakens Romance) acquired a sinister and heartless personality because of the Chess Pieces’ king’s mind control. Unknown to everyone, even herself, Diana’s true kindhearted self is still locked away.
Jackson Jekyll and Holt Hyde (Monster High) are the sons of Dr. Jekyll and Mr. Hyde. When quiet and nerdy Jackson hears loud music, he transforms into Holt, a fun-loving DJ.
When Heckyl (Power Rangers Dino Charge) runs out of energy, he transforms into Snide.
Niki Sanders (Heroes) possesses multiple personalities, most notably "Jessica," due to child abuse as a kid.