'''Basic Trope''': The SplitPersonality is an antagonist.
* '''Straight''': Bob, the shy and kind protagonist, develops a split personality, Evil Bob , who is rude and offensive, and causes problems for all his friends.
** Bob is a saint. Evil Bob is a supervillain planning to TakeOverTheWorld, and doesn't care how many [[KickTheDog dogs he has to kick]] or [[EatsBabies babies he has to eat]] to do it.
** Bob is altruistic to the point that he'd sacrifice his life to save even a wicked person. Evil Bob is a terrifyingly amoral HumanoidAbomination, dead set on exterminating reality.
** Bob is loving and kind. Evil Bob is angry and lashes out at people from time to time.
** Bob's "Evil Side" is just his negative characteristics (anger, pride, etc.) and he has to suppress them.
* '''Justified''': A traumatic event triggered a rage inside Bob that is battling for control.
** Alice is a villain who develops an heroic split personality.
** [[IronicName Evil]] [[DeathbringerTheAdorable Bob]] is a mentor personality who guides Bob to do the right thing to do.
** A traumatic event triggers a split personality inside Bob. This new personality was created to help Bob get through his problems.
** Bob is a StepfordSmiler and his "split personality" is really Bob when his facade breaks.
* '''Double Subverted''': That was a ruse. The new personality is manipulating Bob and giving him bad advice.
* '''Parodied''': Bob has a CompleteMonster in fetus form literally inside his brain.
* '''Zig Zagged''': Bob has four personalities; Evil Bob, who loves to rape children; Mark, a StrawLoser who bluffs to burn people down that used to be Bob's original personality before he had a traumatic incident; Tom, a StepfordSmiler BrokenAce that he developed as a defence mechanism; and Tim, a FriendToAllLivingThings who is a moral compass to Bob.
** Bob only has one personality.
** His other personality is exactly the same.
* '''Enforced''': "How can I add angst to [[MessianicArchetype Bob]], the saint [[AngstWhatAngst who might just well have achieved nirvana?]] Give him an evil personality trying to take over!"
* '''Lampshaded''': "Bob, I will give you an advice. Your worst enemy is yourself."
* '''Invoked''': [[EldritchAbomination Ksogrians]] [[MindRape inflict psychological trauma to Bob]] [[BeingTorturedMakesYouEvil so that he would help their plan to destroy the world instead of fighting against them as the prophecy told.]]
* '''Exploited''': Emperor Evulz uses Bob's evil split personality so that he can brainwash him into a mindless killing machine.
* '''Defied''': Bob seeks professional help, and with the right combination of drugs and therapy, Bob manages to take control of his demons.
* '''Discussed''': ???
* '''Conversed''': ???
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%% Optional items, added after Conversed, at your discretion:
%%* '''Implied''': ???
%%* '''Deconstructed''': ???
%%* '''Reconstructed''': ???
%%* '''Plotted A Good Waste''': ???
%%* '''Played For Laughs''': ???
%%* '''Played For Drama''': ???