Helpless Good Side

So Bob has the heroes on the ropes. They've given everything they had, and it hasn't been enough. Worse, it seems to have just ticked him off more. Things are looking grim. But just as Bob prepares to finish them off, something happens. Suddenly, Bob backs away, first looking confused, then scared. Within moments, Bob has curled into the the fetal position and started crying, begging for mercy, and referring to himself as Tim. Wait, Tim? Congratulations, you've just met the Helpless Good Side.

Sometimes, when a character has a Split Personality, or two people sharing a body, one of them is a total wimp. This can range from merely being incompetent in a combat situation to being unable to take care of their own basic needs, such as feeding themselves and not wetting themselves in public. Regardless, when these come out in a combat situation, the character tends to be royally screwed. If they're on a team, this can transform them from a Badass into The Load. When the Big Bad does this, they may become a Zero Effort Boss.

Compare Good Is Impotent. Contrast Super-Powered Evil Side, which sometimes goes hand in hand with this. Sometimes appears as a result of Easy Amnesia.

Anime and Manga

 * Lunch/Launch of Dragon Ball spends half her time as a hyper-competent, incredibly violent criminal specializing in dramatic robberies. The other half of the time, she's a ditzy, gullible, physically weak woman who is so different from her counterpart that it's hilarious.
 * Animerica's  is revealed to be this, having been intelligent but physically weak compared to his older, stronger, and much favored twin, which made him vulnerable to his Super-Powered Evil Side. He is so much so that he is put in a Driven to Suicide state, believing that he has no chance of redemption after all his actions in Season 2, and his now Enemy Without demon sees this as an opportunity to attempt to take him over again.
 * Lucy of Elfen Lied is a psychotic murderer who can kill things with telekinetic "hands" called vectors that she can extend in a two meter radius around her. However, after taking a bullet to the head, she becomes Nyu, an innocent amnesiac girl who initially doesn't even know how to use a restroom. However, as time goes by, they start switching back and forth.
 * This is strange, but becomes more reasonable when later its revealed that
 * Mibu Kyoshiro of Samurai Deeper Kyo initially appears to be this. Subverted, however, as he is later revealed to be
 * Code Geass R2: After the first showdown at the Sword of Akasha, 's personality reverts to that of herself at the age of ten. Complete with all the skills and confidence of a ten year old.
 * Making matters worse,
 * Also from Code Geass, Chigusa, the side of Villetta Nu that arises as a result of amnesia.
 * Bakura from Yu-Gi-Oh! the spirit of the Ring uses Bakura as a part time body parasite, Bakura generally has no clue what's going on. Bakura is friends with the heroes, while the spirit of the ring is trying to kill them.
 * To a lesser extent Yugi and the Pharaoh, until they come to an agreement.
 * In the Rockman Zero manga, Zero has this in the form of an energy conservation mode. It also takes away his helmet and weapons.
 * A Monster of the Week was a Mighty Glacier Knight Templar member of an order of monks protecting Yusenkio, who came to punish Ranma and the others who 'abused' the Yusenkio curse. However, he'd fallen into one of the springs too, so whenever he got hit with cold water he transformed into a frail ditzy friendly monk.
 * In Sailor Moon S, Hotaru is still present in the mind of Mistress 9 after she takes over her body. She fights against her constantly as she grows weaker and weaker. When her light finally peters out, Mistress 9 announces triumphantly to Usagi that Hotaru has died.

Comic Books

 * A Batman villain known as the Ventriloquist has this... sort of. He seems like a decent-but-timid person, but he expresses his sociopathic side through a ventriloquists' dummy he carries called "Scarface." Scarface is dressed and acts like a miniature version of Al Capone, often giving the impression that he's actually holding his Ventriloquist hostage. If Scarface is destroyed, the Ventriloquist will usually surrender, often expressing relief that the dummy he was talking through and manipulating is gone.
 * However, it's definitely Wesker's own problem and not the dummy being an Artifact of Doom or something (and there are times you'll really start to wonder.) He's been separated from the puppet a number of times, but always winds up with him again in the end. This is typical of Batman's Rogues Gallery - fixing Two-Face's appearance doesn't fix Two-Face for long, etc.

Literature

 * Orion in The Atlantis Complex,
 * Animorphs had a variant of this when Rachel morphed starfish and was split into two Rachels. Her 'Nice Rachel' side was this trope, weak, scared, freezing up under stress, not good for much of anything. However, unlike most examples of this trope, her 'Bad Rachel' side was just as big a liability because she couldn't think of anything more complex than "hit it till it falls over". Both of them realized that as much as they didn't like the other, they needed each other. They worked together, and eventually recombined of their own free will.

Film

 * Ed Norton's character in Primal Fear is at first revealed to have a (not super powered) Super-Powered Evil Side that was probably the one responsible for the murder. After their stunt in the courtroom, with the trial finished, Richard Gere's lawyer character suddenly suspects it was the other way around, that the psycho killer in fact had a Helpless Good Side and he's now helped that psycho use his good side to get out of real jail time. Turns out that's not quite right either as

Live-Action TV

 * Buffy the Vampire Slayer: Ben's presence almost saved their lives as they transformed back into him just before Buffy would have dealt the killing blow and she leaves him alive instead. Too bad for him that Giles is Genre Savvy enough to just take care of the Dirty Business and Shoot the Dog.

Video Games

 * Emil in Tales of Symphonia: Dawn of the New World, who spends the entire game resorting to his Super-Powered Evil Side for every single random encounter.
 * Pearl in Legend of Mana.
 * Some fans of Drawn to Life see  as this to Wilfre.
 * In Nox,, of all people, is revealed to have a Helpless Good Side in the Wizard ending.

Western Animation
"Light!Jackie: (just after he kicks Dark!Jackie, he speaks in a genuinely friendly tone) Dropkicking little girls is not nice."
 * Darkwing Duck combines this with Ghost in the Machine—each character has a "little hero" in them, but villains have said hero Bound and Gagged.
 * In Jackie Chan Adventures, when the Tiger Talisman splits Jackie into two sides, Jackie's light side, often referred to as Pussycat by his darker side, acts much like this. Case in point, he cried when he stepped on a bug. However, as Jackie was Jackie, he's still able to kick ass.