Crossovers
- Child of the Storm has Carol as Harry's in the sequel, after a horrific Trauma Conga Line at the hands of the Red Room which led to him briefly becoming the Dark Phoenix. While there are a lot of candidates for this role, and some initially know him better than she does, she has the advantage of an accidentally created Psychic Link with Harry. This means that she's a very good judge of his actual mood and tends to keep him grounded - either through kindness or Brutal Honesty. As he recovers, this role becomes less necessary (though her death is explicitly what would set him off again), but the likes of Peter Wisdom still see her as something like the Kid with the Leash. It's implied that there's actually an element of truth in this, as his most vicious streak tends to emerge when his loved ones are threatened, and his Courtly Love devotion to her is nigh-total - meaning that while she'd never ask him to do something like, that she most certainly could.
- Unusually, despite their long-running romantic tension, Love Redeems is firmly dismissed. As both agree, they both have far too many issues to date anyone - at best, it would be a horribly co-dependent relationship, with Harry using Carol as a Living Emotional Crutch. They instead opt to leave the door open for something when they're both (particularly Harry) more stable. Lo and behold, in chapter 46 of the sequel, after Harry definitively proves his ability to get through not one, but two major crises while comprehensively resisting the temptation to use his inner Phoenix, and Carol's got over most of her trust issues, they get a Relationship Upgrade.
- In Children of Time, Professor Moriarty tells Dr. Watson that Sherlock Holmes is "drowning" without his Watson. Heartbreakingly true.
- Donquixote Rocinante considers his sister-in-law Evelyn Potter and nephew Atticus as this to his brother Doflamingo in The Emerald Rose
. Doflamingo is still a sociopathic grade-A jerkass, but Rocinante really doesn't want to imagine how he would be without his wife's humanizing influence. - An Extraordinary Journey and other spin-offs establish that in Atlantis's distant past, the Alteran scientist Athena created some of her most devastating weapons after the Wraith killed her younger sister Hera, having previously held herself back on Hera's request.
- Fate of the Clans: An alternate history for Cú Chulainn sees him being ostracized and has numerous attempts on his life (the frequency of poisoning attempts gave him Acquired Poison Immunity) made due to his Riastrad. Emer was the only person who chose to remain at his side and keep him from snapping. When she Takes the Bullet for him and dies as a result, Cú Chulainn begins his murder spree.
- In Incarnation of Legends, Bell is this for Kojiro, who would normally simply look for opponents to amuse himself with. If not for Bell, Kojiro would have simply ignored Haruhime's plight as something that isn't his own business. But Bell's admiration of him instills in Kojiro a desire to prove himself worthy of it that even Ritsuka Fujimaru could not.
- In Is Your Great-Aunt an AI? Harry Potter is the one thing which enables GLaDOS to preserve a sliver of humanity and morals.
- Jaune Arc, Lord of Hunger: Pyrrha becomes one for Jaune as he is gradually corrupted by the Dark Side. Jaune's attachment to Pyrrha and desire to do right by her ends up being the only thing that keeps him from undergoing a full Face–Heel Turn and embracing his worst impulses.
- In Lost in Camelot, Morgana explicitly reflects that Bo and Merlin are the reason she wants to be good after the three form a relationship. When Morgana finds herself thinking about the possibility of just letting Uther die during the Knights of Medhir's attack on Camelot, a talk with Dyson reminds her that Bo and Merlin are too noble to take the option of just not saving Uther even if it would solve their problems, and she wants to be worthy of their love.
- One and Only Son: After Geassing Hamid and learning how he lost his family to war, Lelouch realizes that Nunnally plays this role for him. Without her, he suspects he would have turned out much like his adversary.
- The Pirate's Soldier: Heero Yuy plays this role for Ryoko, much like Tenchi does in her canon series. The story explores it much more in depth as Heero sees a lot of himself in Ryoko and thus tries to push her into becoming a better person.
- Thousand Shinji: In this story Shinji is a psychotic, arrogant, manipulative Jerkass with little empathy. Believe it or not, if his girlfriend Asuka, his surrogate -or so he thinks- sister Rei, his surrogate mother Misato, his friends Touji and Kensuke... he would be way, way worse. Before moving in Tokyo-3 he regarded people as tools to be used and discarded or morons. But after finding them Shinji begins to show love, empathy, tenderness, caring, pity... when he is around them, and he even tries to use his well-trained manipulative skills for the good.
- All Assorted Animorphs AUs shows a few alternate universes, such as "What if David never betrayed them?" and "What if Tom ended up leading the Animorphs?", that make it clear that the Animorphs as a whole are this to each other. In the former, David proves such a frustrating addition to the team that they eventually leave him to die, and in the latter, without Jake as a moderating influence, Marco ends up causing mass human casualties in the name of victory even when this leads to Tobias being killed in the crossfire of the final battle.
- Morality Chain explores a world where Azula cares very deeply for Zuko. This indirectly teaches her enough empathy to maintain a more cordial relationship with her uncle, along with cultivating real friendships with Mai and Ty Lee, rather than simply treating them as servants. She's more prone to Pragmatic Villainy, using the carrot-and-stick approach more than just simply threatening others, and at several times does things purely to make those she cares about happy. All that said, however, it still takes her a long time to work her way towards being good.
- Inverted Macushla, where Stephanie Brown, due to a long series of events, becomes Damian's bodyguard and caretaker/Morality Pet. After Talia al Ghul has Stephanie killed or at least, that's what she tells Damian, Damian joins the Batclan to honor her memory.
- In a series of stories written by WithoutHesitation, Beetlejuice is a complete monster who frequently and indiscriminately commits acts of extreme violence... except when Lydia is around, and only because he doesn't want her to view him in a negative light. Ironically, later in the series it's implied that his relationship with Lydia ultimately resulted in Beetlejuice murdering many, many more people than he would have if he'd never met her, all due to his aggressively possessive and protective behavior.
- In The Bug Princess, Lady Delphine observes that Beetlejuice is unusually benign for a poltergeist. He admits that Lydia "holds the leash" and that it's for love of her that he's so well-behaved, though he adds that the longer they're apart, "the more mindless and chaotic" he's likely to be.
- In Bring Me to Life, Buffy reflects in chapter 27 that she's wanted to punch Kennedy out from the minute she arrived in Sunnydale, and it's only because of Willow that she's restrained herself from doing so. After Kennedy goes off on a Conspiracy Theorist rant, going off about how Buffy may very well be in league with the First and has been plotting to feed the Potentials to Angel to get in good with it, Buffy cuts the chain and decks her. Of course, Willow is just as pissed that Kennedy betrayed her trust.
- In Forgotten, Dracula is perfectly happy to let live humanity as long as his beloved wife is besides him. His servants are not happy about it and decide to kill Mina Hakuba - the latest reincarnation - and destroy her soul to ensure she would be unable to redeem Dracula again. Soma disagrees with it. Quite violently.
- Alucard later begs Mina to teach Soma how to live without her, pointing how she could die from illness or old age and still Soma would fall into the darkness because of it. She promises she will.
- let's go out with a bang!: Kaede is effectively Miu's Only Friend, and the only one she really cares about. Unfortunately, this winds up fueling much of Miu's resentment of her peers, Kaede included; she truly doesn't want to disappoint her. Kokichi, on the other hand, doesn't appear to give a crap what the others think, and constantly provokes, nettles and belittles Miu, leaving her feeling like she's not allowed to defend herself against his abuse without being treated like she's the bigger problem.
- In All You Need Is Love Naomi Misora realizes, to her horror, that she's the Morality Chain, so she sticks around Light even while knowing he's a manipulative, narcissistic, mass-murderer because she knows he could be so much worse.
- In A Cure for Love, L becomes Light's Morality Chain. Even after Light regains his memories he shows more restraint as Kira than he did before (to the point that a fellow Knight Templar thinks he’s gone soft) and Light even considers L to be his "partner" in destroying another enemy. But then when L "betrays" Light by suggesting he should be committed; Light snaps, abandons any remaining moral constraints, and essentially takes over the world in an afternoon.
- In Fate/Starry Night, Jack would have gone on a killing spree in Fuyuki if not for her fear of being scolded by Ritsuka, instead venting her impulses on the mud copies of him that have been sprouting up around the city.
- Molly Weasley is this to Harry in the one-shot After The Final Battle. Harry easily admits to himself the only reason he doesn't kill Ron is because he knows it would devastate her and she's the only adult who's ever acted like a parent for him. Especially after seeing her boggart (which shows a person's greatest fears) is her family dead, which includes Harry.
- In Fate's Favourite, Harry serves as this for teenage Tom Riddle, who considers Harry to be his equal and his best friend (despite having that pesky moral code) and does not want to make him too upset.
- In Hail Odysseus, James Potter's shade heavily implies that a Slytherin Ginny Weasley serves this function for Harry.
- In He Is Not One of Us, Snape finds out that Harry is secretly studying the Dark Arts and advises him to keep some humanity in order to avoid their seductive aspects. Harry replies (referring to Hermione) "She's outside the door."
- An Invoked Trope in Heir when Voldemort worries about what kind of monster he might become without Severus.
- In If Them's the Rules, a Time Travel fic where Harry raises young Tom Riddle. Tom is still a Sociopath but he behaves himself out of loyalty to Harry because Harry is the only person to ever show him kindness.
- In Kaleidoscope of Magic Hermione becomes the one thing keeping Harry gray-not-dark after Dumbledore and Algernon Croaker throw him into Azkaban and have him tortured to give him a superpower which only awakens in response to extreme misery.
- In Starfox5's Reformed, Returned, and Really Trying, Gellert Grindelwald tries to stay on the side of good, but his idea of ethics is largely "things Albus said to do."Unfortunately, none of the remains had been in a condition to be repurposed as Inferi - no, wait, Albus had been quite clear about how that wasn't acceptable.
- In Serenity, Tom Riddle snapped and became an Omnicidal Maniac after unintentionally killing Myrtle with the basilisk.
- Zigzagged in Cultstuck. Karkat is Gamzee's moirail, and Gamzee sobers up, which makes him evil, so he can protect Karkat effectively. During Gamzee's POV chapters, his love for Karkat is basically the only thing keeping him coherent. The creepiness of this is not ignored.
- In A Thing of Vikings, Heather basically asks Fishlegs to be this for her when she realises that she needs more than just herself in her role as Berk's spymaster, wanting to ensure that she doesn't end up like Alvin.
- In the AU fic What Lies Beneath, just meeting Hiccup disrupted the Queen's hold on the Night Fury, so he remained with the pack out of choice rather than her control.
- In Some Semblance of Meaning, heroine Vale holds onto the promise she made to her younger sister that she wouldn't sacrifice her morality in the arena, whenever she considers doing anything morally reprehensible (not that such a Shrinking Violet would probably start chopping her friends and allies to pieces, anyway, but her promise to Laurel ensures it). An even better example would be the way that Vale herself serves as a Morality Chain to Obsidian.
- In Gaz Dreams of Genie, Dib turns out to be this for Professor Membrane. In the new reality Gaz creates by accidentally wishing Dib was never born, the Professor's disappointment at his only child being an apathetic video game junkie causes him to give up on humanity and become The Quisling to the Irkens after they conquer Earth, saying with comedic specificity that if he had a child like Dib he wouldn't have.
- In The Ronless Factor, while nobody else considers Kim evil, after learning that Drakken and Shego were responsible for Ron's death in a recent car crash, she expresses concern that she could actually be capable of killing them both when she next sees them, recalling how she almost killed Shego by kicking her into the Diablo control tower in their last confrontation. This is the main reason she asks Bonnie (and, by extension, Ron, who has come back as a ghost that only Bonnie can hear) to join her on her next mission, as she wants someone there in case she goes "crazy" and does too much damage.
- In Because I Knew You, hearing Peter talk about how his aunt May was this for him helps Wanda realise that she avoided searching for a reality with Vision and her sons in it because she knew that any version of Vision would be ashamed of what she’d done even if he wouldn’t have outright condemned her for it.
- In Spider-Man: Finding Home, Peter serves as one for Yelena Belova and Felicia Hardy in particular. While he accepts that Yelena in particular sometimes has to kill her opponents, such as when she killed Kraven the Hunter so that she could take back the stolen White Tiger amulet and use it to help Peter, he inspires both women to recognise when they don’t have to go that far.
- In Mega Man Reawakened, Robert was this to Tron when he was human. When she finds out he's still alive, she turns good. Later it's reversed, with Tron helping to keep him on the straight and narrow.
- In Fox Rain, Trixx acts as this to Lila, keeping her from her canonical descent into villainy by giving her the courage to not become a shut-in and fester on her anger and later warning her she was being manipulated by Papillon into mistrusting all her friends.
- Hero Class Civil Warfare: Secretly, Izuku intended for this to be Shinsou's true role on the Villain Team: acting as a leash on Izuku and the others to help them avoid getting Lost in Character. Ironically, the inverse happens when Shinsou learns about the fifteenth objective.
- Mastermind: Rise of Anarchy highlights what happens when one of these dissolves; the 'Bakusquad' broke up after learning the role Katsuki played in creating Mastermind. Without them as a stabilizing influence, Katsuki grows increasingly unhinged — though Tokoyami notes that he might simply be 'revealing his true character' instead.
My Little Pony: Friendship Is Magic
- Aftermath of the Games: Integration reveals that this is why Princess Celestia takes on personal students. Due to her incredibly long lifespan, she worries about losing sight of what kind of impact her decisions make; having students helps keep her grounded. She intends to have Luna and Cadance start taking on students of their own once they're ready, and wanted to discuss the matter with Twilight before she did the same.
- In Diaries of a Madman, Taya and Flo often act as this for Navarone, putting a damper on some of his more unethical behavior.
- Inner Demons: In a way, Trixie serves as this to Queen!Twilight, as the former's Undying Loyalty brings out what little compassion and good is left in the latter. When Trixie dies, Queen!Twilight suffers a full-blown Villainous Breakdown and shifts from an Evil Overlord to an Omnicidal Maniac.
- Fluttershy becomes this for Rainbow Dash in RainbowDoubleDash's Lunaverse, as Rainbow Dash in this continuity never became the Element of Loyalty, thus never forming the True Companions like in the main story. This also deconstructs this trope in that with just a Morality Chain and no one else, she is unable to extend that sympathy to other people or really relate to them.
- Itachi becomes this to Sasuke in Son of the Sannin, always working hard to keep him from losing his path.
- In Voiceless, the Third Hokage seems to be this for Naruto. In the fourth chapter, the narration mentions how he sometimes despises Kakashi, and frequently thinks of leaving the village due to not having any other attachments.
- In Advice and Trust, Rei is the one thing keeping Kaworu from giving into his Angelic instincts and becoming Tabris. When she dies in a Heroic Sacrifice against Armisael, it's only thanks to a combination of his knowledge that she usually gets better in other timelines and a well timed pep talk from Mrs Horaki that keeps him from trying to start Third Impact right then and there.
- A Crown of Stars:
- In chapter 52 Shinji realized he was just like his father and he would also burn the world for the woman he loves. So that he asked Asuka keeping him from becoming a monster.
- Shortly before Asuka had wished punishing a bloody dictator and rapist with extreme prejudice, but she held back because she thought that Shinji -who hates hurting people and killing- would have a trouble with punishing him too severely.
- In A Monster's Marriage, Jaune is married to Cinder Fall. His genuine kindness actually rubs off on Cinder, making her slightly less of a controlling bitch. Even Mercury and Emerald find themselves feeling like normal people when interacting with Jaune. By the end of the story, he shifts fully into being a Morality Pet, as he is made privy to the truth that many of his close friends are criminals, and starts actively rather than passively working to improve their lives.
- In Freedom's Limits, Madavi appoints herself as one to Smador, trying to encourage or help him to find alternate paths other than stealing and killing to survive so he won't end up like the more savage orcs, who act more like animals and often wind up dead one way or another.
- In Transformers Meta It's Personal Hound inwardly directly states that Bumblebee is this to Grimlock while he is contemplating their friendship.
- The Roboutian Heresy: In this timeline, Konrad Curze had one in the form of an elderly widow who adopted him and taught him compassion and mercy; thus, while he still became a brutal vigilante, he never became the sadistic butcher known as the Night Haunter, and regularly returned to her to confide in her after each criminal he killed. In the 41st millenium, the modern Night Lords Legion, having never become traitors, have expanded this into the station of "Sin-eaters", mortal crew who act as a combination of therapist, confessor, and confidant to the Night Lords; as the Eight Legion are still responsible for doing the Imperium's Dirty Business, even as loyalists, this helps them stay sane, moral, and in control, rather than becoming the merciless serial killers they were in canon.
- In the Better Bones AU, Russetfur's death causes Blackstar to be manipulated by Sol, reverting to his old ways of being a follower of someone with questionable morality.
