Basic Trope: Character is the main or sole reason that another character remains good.
- Straight: Alice keeps her older brother Bob's nastier side from surfacing.
- Exaggerated: The only thing keeping Bob from gleefully skipping across the Moral Event Horizon is Alice.
- Downplayed: Alice keeps Bob from being an aloof and condescending Jerkass.
- Justified:
- Alice and Bob have Twin Telepathy and Alice is an empath. She routinely sends Bob positive emotions to keep him in check.
- Bob had a very traumatic upbringing, and as a result hates everyone and everything except for Alice.
- Bob swore an oath to Alice, and he is not looking forward to break that oath.
- Inverted:
- Corrupt the Cutie.
- Alice softens Bob's nastier side, turning him into a better person over time.
- When Bob dies, Alice begins to turn evil because she starts going insane.
- Alice is the only person who keeps Bob evil. When Alice dies, Bob can finally become the nice, just person that he is inside.
- Alice's death from another villain leads to the villainous Bob forming an Enemy Mine with the heroes to avenge her, eventually leading to a Heel–Face Turn.
- Subverted:
- When Alice is killed, Bob becomes even more devoted to fighting for good in her memory.
- Alice tries to keep Bob from committing evil acts, and fails every single time.
- Double Subverted:
- Bob tries fighting for good but he actually becomes brutal and obsessed with vengeance.
- After failing to convince Bob not to burn down a church, rob a bank, kill a priest and kick a puppy, she manages to convince him not to jaywalk.
- Parodied: Bob is a psychotic, Spikes of Villainy-wearing Sociopathic Hero who turns completely harmless when Alice is around, and Alice refuses to believe he's anything else.
- Zig Zagged: Alice's presence prevents Bob from committing evil deeds half the time; it has no effect on him at other times.
- Averted: Alice's presence has no particular positive effect on Bob's behavior.
- Enforced: The director says he can't see why Bob is on the good guys' side when he's much meaner than any of them, so the writers add Alice to give him a reason to stay.
- Lampshaded:Bob: Now that the meddling fool is out of the way, I'm going to kill you!
Alice: Bob, what are you doing?
Bob: ...Nothing!
Alice: Good. If you hurt him, I'll be disappointed in you. - Invoked:
- Alice was deliberately raised to be her brother's keeper and balance out his bad side.
- Bob seeks out good people to ally himself with, knowing they will curb his violent tendencies.
- Exploited: The heroes set Bob up with Alice in order to keep him under control.
- Defied: "What, you thought I'd spare you because my little sister was around?" *click KA-BLAM* " You just couldn't get it in your head otherwise."
- Discussed: "I always feel like Bob would kill us the moment our backs were turned if Alice wasn't around." "That sounds like a ticking time bomb to me."
- Conversed: "He's one of those characters that only stays good because his sister is watching. I bet they'll kill her off or something eventually so we can see him really snap." "But this show is not clichéd in the slightest, and Alice does have her own story. I highly doubt she'd die for the sake of cheap drama."
- Deconstructed:
- 1.)Because she has to keep Bob in line all the time, Alice can't live out her own life and is just as chained to his side as he is bound by her existence. Mutual resentment gradually weakens the bonds between them until something finally gives way.
- 2.) Bob only allows Alice to moderate his behavior because his long-term goals hinge upon maintaining her trust and goodwill. Once his short-term goals are completed and You Have Outlived Your Usefulness, all bets are off.
- 3.) Just because Alice is there to prevent Bob from turning bad doesn't mean that Alice herself is pure good. She is just as flawed as Bob, if not more so. In other words, Alice can be scarier than her brother.
- Reconstructed:
- 1.) Eventually, Alice rubs off on Bob; he starts to become a genuinely good person even when she's not around, so eventually, he doesn't even need a morality chain to be a good person anymore. Thus, Alice can spent time away from him without worry or guilt. But they still time lots of time together, just for fun.
- 2.) After he thinks he no longer needs Alice, Bob starts misbehaving and surprises even himself when he still listens to her later. Whether by coming to sincerely value her goodwill and friendship, fraternal instincts overpower him or Alice stringing him along in some other way, she continues to moderate his behavior.
- 3.) Bob eventually notices Alice's flaws and decides to keep her nastier side from surfacing. Everyone Has Standards, after all.
- Played For Laughs: Alice keeps Bob in line by terrifying him, despite being The Cutie in all other respects.
- Played For Drama: Alice is targeted by people aware of how important she is to Bob in order to get Revenge by Proxy.
The only reason I'm letting you live long enough to go back to Morality Chain is my sis, got it? Anything happens to her, I'll kill you, grind you into hamburger, and feed you to your mother, and if you're lucky, it will be in that order.
