In Bambi II, Bambi has been sent to live with another doe after his mother's death, despite vigorously wanting to stay with his father. Later, the doe gets caught in a hunting snare with vicious dogs making a beeline for her. Despite the doe actually begging Bambi to run and save himself, he chooses to distract the dogs onto him and save her life. The fact that her telling him to keep running mirrored what his mother said to him before she died probably helped him come to his decision.
Anastasia in the Cinderella sequels is gentle, kind, and free-spirited when not around Cinderella or her mother and sister. Cinderella helps bring this personality out into the open.
This reaches its apex in Cinderella III: A Twist in Time. When Anastasia (who's been rewritten as misguided young woman who wants love more than anything) gets her hands on the Fairy Godmother's wand, she gives it to Lady Tremaine, who realizes its Reality Warper potential and rewrites history so that Anastasia, and not Cinderella, fits the glass slipper on the day of the Prince's test. At first, Anastasia is thrilled — she finally has her Prince Charming — but as the movie progresses, she starts feeling guilty. Lady Tremaine tries to avert this sudden conscience by brainwashing the Prince, turning Anastasia into an exact copy of Cinderella, and making sure the real Cinderella is put in a Death Trap during the royal wedding. But Cinderella manages to escape and return to the wedding, when it comes time for the vows, Anastasia — who, for all intents and purposes to the entire world, is Cinderella at this point — can't bring herself to say "I do." To Cinderella's amazement, Anastasia says "I *DON'T*". She explains that she wants to be loved for herself, even if that means losing everything she thought she'd ever wanted. After her mother has been dealt with, and Anastasia returns to her normal self, Cinderella, seeing her remorse, forgives Anastasia and finally repairs their strained relationship, and the two can finally enjoy each other's company again without Lady Tremaine on their backs.
Played straight later on when Kuzco wanders off into the jungle, despite Pachas warnings. Pacha could easily leave him to die, since Kuzco still wants to destroy his village and refuses to change his mind. He even considers it for a moment, but ultimately his conscience gets the better of him.
Defied to some extent in The Hunchback of Notre Dame; the Archdeacon is trying to convince Judge Frollo that he should spare Quasimodo after killing the child's mother. Frollo is initially dismissive, but changes his tune after the Deacon says that while no mortal would know, killing a child before the steps of Notre Dame would certainly draw God's Wrath (in essence, there is never a moment where he or anyone else is truly alone in the dark).
Played straight twice later on with Quasimodo deciding to help Esmeralda. The first time involves Frollo telling Quasimodo that he's planning on attacking the Court of Miracles and the second is during the climax, the latter being a more classic example of the trope as Quasimodo has just told the gargoyles to leave him alone.
Quasimodo: Me? What am I supposed to do? Go out there and rescue the girl from the jaws of death and the whole town cheers like I'm some kind of a hero?! She already has her knight in shining armor and it's not me! (sighs) Frollo was right. Frollo was right about everything. And I'm tired of trying to be something that I'm not.
In Incredibles 2, Winston has a golden opportunity to escape from the yacht Everjust, which has been set on a collision course with the city, and no one would know that he hadn't been kidnapped by the villain, his sister. Instead, he jumps back on the boat, risking his life to save the civilians and heroes trapped aboard.
Invader Zim: Enter the Florpus: Professor Membrane spends the last act of the movie convinced that everything bizarre around him is just a hallucination brought about by being hit on the head, and is thus completely cavalier about the situation since he's sure it's not real. Despite this, he still takes the time to assure a panicking Dib that he's always been proud of him, and when it seems that Zim's Mecha-Mooks are about to kill Dib, he goes full Papa Wolf to fight them off and protect his son.
The Iron Giant: When Hogarth first encounters the Giant, he witnesses it accidentally tangling itself up in and getting electrocuted by power lines out in a secluded power station after dark. Terrified out of his mind, he has a chance to run home through the woods in the dark with no one the wiser, not even the Giant. However, as he hears it screaming in pain he realizes that he can't leave it to suffer, and so risks his own personal safety to shut off the power to save its life, despite still thinking its dangerous and having no expectation that it'll notice or feel grateful later. (Thankfully for Hogarth, itdoes.)
Moana gives us something sweet at the start. Baby Moana is down at the beach and sees a pretty seashell and really wants it, but she sees a little baby turtle scared of the birds trying to eat it as it's trying to get to the water. No one would blame her if she were to just get the shell at that age, but Moana grabs a leaf and protects it from the birds, losing the shell in the process. This is what makes the ocean choose her.
In The Peanuts Movie Charlie Brown winds up getting the perfect score on a test. Because of this, all the kids in school and town, barring Lucy, view him as a genius, which earns him a large amount of popularity. During an award ceremony for passing the test, he discovers that he and Peppermint Patty accidentally signed their names on each other's test sheets when they were rushing to turn the papers in - she's the one who really got the perfect score. He's the only one who knows the truth, and if he wanted to could continue to keep it a secret, keeping his newfound popularity in the process. Instead he confesses the screw-up to everyone and tells them that Peppermint Patty was the one who aced the test. This turns out to be one of the main factors to winning the Little Red-Haired Girl's heart.
The Rescuers has Bernard singing the RAS anthem by himself just outside the meeting hall. When Bianca sees him doing that, that is enough proof for her of how deeply he values the organization's ideals. Bernard was merely the janitor at the time, and the other representatives/agents who were in the meeting hall were being far less reverent of the anthem. Also, it was Bernard who suggested that it wouldn't be safe for Bianca do the mission alone, showing that he cared for her.
In Sing, Johnny, desperate for the cash to pay his father's bail from prison, secretly breaks into Buster's office to steal the prize money. But he changes his mind when he sees Buster's notes on his profile — namely, the "Natural born singer" part.
Disney's Tarzan has Clayton give Tarzan the choice of shooting him with his own double-barreled shotgun with no one else around: "Go ahead, shoot me, be a man". Tarzan's reply? Mimicking the sound of the gun being shot to put some fear into Clayton before smashing said shotgun in front of him. "Not a man like you."
Xuan is notably surprised about Blanca being a snake demon but still risks his life to save her, despite the fact that betraying her to the army would leave him better off.
Despite wanting to leave Blanca in poor conditions and then running away after Xuan refused, Dudou ultimately returned out of loyalty to him.
Xuan keeps his promise to rescue the villagers from a rampaging Blanca even though said villagers turned their backs on him for now turning into a demon.
Verta, the one who was trying to keep Xuan away from Blanca, kept the jade hairpin that held the memories of him in order to give it to Blanca someday.
2 Days in the Valley: A car thief who sees Allan rolling on the ground in the middle of the road pauses his crime (after momentarily hesitating) to help Allan out of traffic (which draws some attention) and then drive him to the hospital.
In the final scene of 3:10 to Yuma (2007), after an entire movie of everyone trying at great cost to bring Ben Wade in to justice aboard the titular train, every single character of significance is dead or dying, including Dan Evans, except for Ben himself and Dan's son William. After a brief moment holding Ben at gunpoint, William turns his back on Ben to instead be with his father in his dying moments. Since Ben's late gang wiped out basically the entire police force of the town in their efforts to break him out, there's pretty much nobody left who's still hunting him and absolutely nothing stopping Ben from stealing a horse and riding out of the town to eternal freedom. He willingly climbs aboard the train and locks himself in a cell anyway.
In Aliens the commissioned officer Gorman spends most of the movie as a weak, ineffectual ditherer. At the end, when faced with the decision between relative safety and going back for Vasquez by himself despite the obvious consequences, he decisively chooses the latter.
Spoofed in Avengers: Age of Ultron during the climatic battle of the movie, when Hawkeye gets annoyed by yet another one of Pietro's taunts. He jokes that he could shoot Pietro in the back right now and no one would ever know, then lowers his bow. Though, not before sarcastically grumbling about it before jogging to rally point.
Clint: "Nobody would know...nobody. 'Yeah last I saw him an Ultron was sitting on him. Yeah he'll be missed, that quick little bastard. I miss him already.'"
In Batman Begins, during the movie's dramatic action climax aboard the train, shortly before it's about to crash and explode, Batman manages to knock his former mentor Ra's al Ghul down to the ground during their fight. The trope begins when Batman has the chance to escape and survive the crash. Nobody will know what happens here, and he chooses to take his revenge by simply allowing the baddie to stay and die, while Batman escapes. In Batman's words: "I won't kill you, but I don't have to save you.".
In Black Panther (2018), M'Baku and his men save a critically injured T'Challa despite the fact their last encounter was them fighting and the former had no reason/benefit to do so. Later when T'Challa's family comes seeking help, M'Baku could have easily hidden T'Challa's presence but chose to do otherwise, even when T'Challa's family came and initially offered him the herb and a golden opportunity to become king.
This trope is discussed in City Slickers. To paraphrase the conversation: "Okay, you're married, but suppose a gorgeous woman came from a spaceship and wanted to have sex with you and leave without anyone knowing. Would you do it?" "No." "Why not?" "Because that happened to my cousin, and the women at the hairdresser's shop found out about it because they know everything!"
It's brought up again, and when pressed, Billy Crystal's character admits that he wouldn't do it, even if there was never a chance his wife would know about it. When asked why, he says "Because I'd know about it!"
In Clerks, Dante leaves a relatively unsupervised pile of money on the counter in the store for change and payment of goods, with a sign next to it that encourages the customers to "...leave money on the counter. Take change when applicable. Be honest." Dante is actually on the floor behind the counter with his girlfriend, inattentive of his job. She asks how he knows that they taking the right amount of change or are even paying for what they are taking and he responds with something like "Theoretically, people see money on the counter and no one around, they think they're being watched."
In Con Air, Cameron Poe is given the option of escaping when the plane is hijacked by criminals, he is after all an freed man who already served his sentence. He opts to stay because his best friend will die without his insulin shot and he stays along so he can get one. He also mentions being unable to live with himself if he allowed the only female guard on the plane being raped and killed by the local sex offender.
The Defiant Ones follows Chained Heat escaped convicts Joker and Noah to the house of a sexy but lonely abandoned housewife (who is never named). After the housewife and Joker go mattress dancing, she offers to drive Joker away in her car, while directing Noah to a shortcut through the swamp to a place where he can catch a train. Once Noah leaves, the housewife casually admits to Joker that the route through the swamp is a death trap, which she sent him to deliberately so he'll be killed before he gets a chance to squeal. Joker has the chance to run away to freedom with a hot, horny woman who has a roll of cash as well. He abandons her and instead goes to save Noah.
Enough has the final showdown between Slim and Mitch where she gets the edge over him, he gets himself knocked out cold and while she has an opportunity to behead him, she stops at the last moment, crying to her best friend on the phone that she's not a killer. This works against her as Mitch regains consciousness and knocks her out with a lamp from behind. As he then tries to finish her off, she wakes up and ultimately dispatches him via a Railing Kill.
The Front: Under pressure to "name names" before HUAC, Howard is told he can get off easily by naming Hecky, who is dead. No one would care, and no one thinks Howard is a sympathizer. Rather than take the easy way out, Howard tells the committee off to honor his friends, leading to his imprisonment.
Halo: Nightfall: It becomes increasingly clear that only two people are going to get off the ring. Locke and Randall assert "Lifeboat Rules," where until that decision has to be made the entire team works as though everyone will make it. This does not turn out well, as the backstabbing starts soon and almost everyone but Locke and Randall crack under the pressure.
In Hannibal, Lecter is at the Big Bad's mercy, about to be fed to a pit of wild boars, when Lecter raises an interesting question to his personal physician:
Hannibal: Hey Cordell! Why don't you push him in? You can always say it was me.
The physician does. This must be one of the only times in the history of fiction that killing somebody who is helpless in your care and then setting free a killer like Hannibal Lecter is actually the heroic choice.
In Happy Death Day, protagonist Tree is stuck in a "Groundhog Day" Loop where every day ends with her getting killed by an unknown masked figure... and, even worse, she keeps coming back with residual damage from what killed her previously, suggesting that she may eventually 'run out' of opportunities to keep re-doing everything. At one point in the film, she has a chance to kill the man she has identified as her apparent killer, but since he has killed Carter- a boy Tree only met the day before the loop began- when Carter tried to save her life, Tree instead kills herself to bring Carter back, despite not knowing if this will be the loop where she finally takes too much damage.
Could be argued that Carter had a similar opportunity; he tried to save Tree's life and got killed for it, with Tree commenting in the next loop that she can't believe he did that for her.
In Harry Potter and the Goblet of Fire, while the Second Task is the same between book and movie, the climactic Third Task, a maze where the enemies are dangerous magical creatures, is replaced with a shifting maze, in which the enemy is human nature. Harry is given the temptation of letting Cedric be taken and subdued by magical vines and guaranteeing winning the Triwizard Tournament, but he instead chooses to save Cedric, possibly costing him the tournament victory as a result.
Chris Mannix in The Hateful Eight. When he is given the chance to execute confessed murderer Joe Gage in cold blood, he immediatly declares to be completely willing to do so. However, a minute later, when a shootout happens, he is wounded, and he could still shot Joe Gage not even so much in cold blood at that point, he backs down from doing it, because Joe Gage just reminded him that he is unarmed. Clearly, Chris Mannix hates the idea of execute an helpless target, even at risk of his own life and even if he would apparently want it.
In Heathers, Alpha Bitch Heather Chandler is only seen alone during a single short scene in the entire movie. In it, she takes a drink in the bathroom mirror, then spits it out at her reflection.
Bilbo has the chance to kill Gollum and no-one would know about it. He doesn't.
Another one happens to Bilbo when he overhears the dwarves talking about Bilbo deserting them after escape from the goblins. Since he is wearing the Ring and thus invisible, he could have let them believe he was gone for good and could have gone home back to the Shire. Instead, he reveals himself and continues the journey with them.
Villainous version: Sebastian Caine in Hollow Man has quite a bit of unspoken Inner Monologue about this trope and concludes that "It's amazing what you can do... when you don't have to look at yourself in the mirror any more." He finally crosses the line when he sees his lax-about-closing-her-shades-while-changing neighbor while he's invisible. He pulls off one of his latex gloves and asks himself "who'll know?" It's shown that he messed with her and got at least a good look at her naked, and a deleted scene shows he raped her.
Horrible Bosses: While the bosses are terrible people who have made the lives of the protagonists a living hell, once the plan to kill them goes into gear, both Dale and Nick (albeit the latter more reluctantly) admit that they can't bring themselves to actually commit murder. Though luckily for Nick, Harken was more than willing to do it for him.
In the 1965 comedy How to Murder Your Wife, Jack Lemmon is on trial for murdering his wife. When the trial appears to be headed for a conviction, he takes up his own defense and pleads justifiable homicide, appealing to the all-male jury's frustrations regarding their own wives. He offers a witness (and thus the jury) the idea that if they could press a magic button and their wives would disappear and no one would know, would they do it?
Played for drama in Kingsman: The Golden Circle when The Hero Eggsy is instructed to seduce a female minion of the Big Bad so he can put a tracker on her, while he is very devoted to his girlfriend Tilde. Instead of doing the deed and never let her know about it, he decides to call her to get her approval first. Naturally, she takes this badly and breaks up with him. This ends up leading to her taking drugs to cope with their break-up, which were poisoned by the Big Bad and nearly leads to Tilde dying.
The whole point of Logan. The title character wants nothing more to do with being the superhero Wolverine and wants to live a normal life. Then, he meets a girl who went through the same experiment performed on him and looks after her with the promise of a large sum of cash for doing so. Once he is paid, no one would blame him for just leaving; however, after a "The Reason You Suck" Speech from the girl, who is for all intents and purposes his daughter, he decides to risk his life to keep her and her "siblings" from being recaptured and used as deadly assassins, proving that he still is a hero.
In Lord of War, Jack Valentine keeps Yuri Orlov from being killed after being almost busted for gun running to Africa by citing this trope to his partner (who was suggesting they just kill Orlov).
"Look at where we are! Who will know?"
To elaborate, it's a rarer variant of the trope, where the one proposing to go in the dark isn't a Big Bad, but actually a Bit Character serving as a Foil to Valentine's integrity, and he doesn't propose it to The Hero.
The Long Kiss Goodnight: At one point, Charly contemplated on killing both Hal and Caitlin in order to eliminate any traces of her Samantha persona, but she finds herself unable to do so.
During the latter portion of Mad Max: Fury Road, Max has the complete choice up to him, without it being a last resort or survival necessity like it was in the previous films. Once the Vuvalini, Furiosa and The Wives give him a motorcycle as a reward for helping them, he can either let them go to what is likely a barren wasteland, and they would never hate him for it. Or he could go after them and help them achieve a more hopeful future, without expecting any more reward for it. He chooses the latter.
In The Martian, at one of several stages where everything goes to hell, the camera cuts to the chief scientists of the Chinese space program, where they discuss how their classified boosters could help, but if they didn't, the world would never know. After a few more lines, the film cuts straight to the director of NASA taking their call, and the boosters do indeed play an important role in the eventual plan.
Memento. Because the protagonist can't remember anything for more than a few minutes lots of people are rude to him or openly take advantage knowing he won't remember. Including himself.
In The Mummy Returns, Evelyn O'Connell and Anck-su-namun show what they truly are when faced with their lovers, Rick O'Connell and Imhotep, dangling on the edge of a pit into Hell while trapped in a collapsing temple. Even when Rick is yelling at her to get to safety, Evelyn refuses to abandon Rick and risks death to run to the crack and pull him to safety, while Imhotep, who has suffered a horrific living death for over five thousand years due to his love for Anck-su-namun, begs her to help him and she runs away because she might not make it.
Bernard from Old School. Even though he was the one with the idea to start a fraternity and the one who talks and raves about the fun they'll have, he's still the only founding member who's married, and he successfully resists temptation during a frat party by refusing to sleep with a college girl who was more than willing.
In Pitch Black, Riddick tells Johns to kill him in cold blood ("That's what I'd do to you."). An interesting case because the villain is effectively trying to commit suicide-by-hero. Subverted because Johns only ignores him because Riddick's bounty is worth double if he's alive, and it's strongly implied Riddick knew how he'd react.
Later in that film, Riddick does the same thing with Fry. "Nobody will blame you. Save yourself, Carolyn."
The Purge: When you have an event in which you can literally get away with anything for 12 hours, it really tests your character.
And in one instance, after suffering at the hands of one extremely vindictive Purger, his victim purges him AFTER the 12-hour period is up. The only other victim decides to stay quiet about it.
Red Rock West: Michael repeatedly passes this test. He tells the truth about a disability he has on a job questionnaire. He doesn't take money sticking out of a cash register when he's alone in a room with it. And when he accidentally hits a man in the rain, he ultimately goes back to check on him and takes him back to the hospital in spite of how much danger is waiting for him back in town.
Tom Hanks' character plays this off ingeniously in Road to Perdition, covering his getaway from a heist by convincing the bank manager to take some of the loot from the bank robbery for himself. "You can always tell Chicago (Al Capone) that I took it."
In Rush Hour 2, Jackie Chan's character Lee has the Big Bad against the wall all alone and at gunpoint, and given what the Big Bad has done and the effect it had on Lee's life, none would blame him for shooting the guy where he stood. Chris Tucker's character James Carter enters this scene as the angel to the Big Bad's devil, telling Lee to not go too far. He then subverts his role after the Big Bad insults the memory of Lee's father, and tells Lee to shoot the guy. Lee still doesn't do it.
Half the plot hinges on Miller and his squad's willingness to pursue what by all rights is a suicide mission. They could have easily just scrubbed the mission and said they couldn't find Ryan, but they ultimately decide to see it through to the end. In the climax of the film, they choose to stay and defend a bridge against massive odds, even going beyond their orders, because the call of duty demands it. And most of them pay with their lives for it.
Miller's squad comes across a German machine gun nest set up to ambush any approaching American soldiers. His squadmates point out that they can easily bypass the Germans, but Miller decides to take it out to prevent any more Americans from being ambushed.
After the aforementioned firefight, they capture a German soldier and could easily execute him on the spot, but decide to take mercy and let him go; in an evil example of this, that German soldier who before pitifully grovelled to the Americans for his life, turns up at the Final Battle and shoots Captain Miller without hesitation and then tries to surrender to Upham when The Cavalry turns up. Upham shoots him dead.
In the Andrei Tarkovsky film Stalker, the Room is a special place that grants the innermost desire of whoever walks into it, regardless of whether that person is conscious of it or not. Do you really want to know what your deepest desire is, and do you dare find out? Porcupine, a man who allegedly found the Room as eventually Driven to Suicide because he went into the Room to wish for the resurrection of his dead brother, but the Room instead granted him a vast sum of money; he killed himself because he couldn't live with the realisation that he wasn't as noble as he thought he was, that he wanted to be rich more than he wanted his brother to be back.
Also in Revenge of the Sith, when Padmé is alone with Anakin on Mustafar following his FaceHeel Turn, he offers her the chance to rule the galaxy at his side once he's overthrown Palpatine, saying that they could "make things the way [they] want them to be" and that they can finally be together openly. Padmé proves to be as incorruptible as Luke, as she doesn't even seem to consider accepting his offer and says she can't follow her husband down this path.
One of the many ideas of Shame concerns Brandon expressing his carnal desires without anyone in his close circle finding out. It acts as a Freudian Excuse however because of his and Sissy's childhood.
Invoked by Past Charles in X-Men: Days of Future Past. During the climax, Hank urges him to put Mystique out of commission so she won't kick-start the Bad Future. However, Xavier refuses to do this because Mystique has spent her life being influenced by others, so instead, he tells her that he will do nothing to stop her, but hopes that she will see there is a better way. She agrees and stands down.
Charles: I have been trying to control you ever since the day we met, and look where that's got us. Everything that happens now, is in your hands. I have faith in you, Raven...
Z-O-M-B-I-E-S (2018): In Z-O-M-B-I-E-S 2, when Zed returns the necklace the werewolves gave Addison and she assumes he just found it, he could've played along with her assumption but decides to admit he stole it when she wasn't looking.