In The Batman Adventures (during the The New Adventures period), a multi-millionaire philanthropist places a million dollar bounty for the Joker's head (dead or alive, but preferably dead), in order to have justice for the Joker killing his son. He does so via live broadcast, including the Times-Square-esque television screens in Gotham Uptown. The whole city goes berserk as everybody tries to capture and or kill the Joker. Finally, Batman kidnaps the millionaire, brings him to a dark corner of Gotham where the Joker is tied to a chair in a cone of light. Batman says that he will not allow the man to buy himself a murder; if he wants Joker dead, he is going to have to kill him himself. Before disappearing into the dark though, Batman asks the businessman if this is really what he wants, and if it is really worth it. The man, alone with Joker, begins to lunge at the clown to strangle him, but stops himself, unable to go against his humanitarian nature. The next day, he withdraws the bounty, instead using it to start a support organization for the families of victims of violent crime. Just like Batman expected he would.
In one story, a child kidnapper called Playground snatches a young girl off the streets, but she is able to escape him and goes hunting for a heroine like Batwoman or Huntress to help her. Instead, she runs into Poison Ivy and Harley Quinn, who are planning to break into a bank. At first, they tell her to scram, only for her to reveal she has bruises. Despite having lost her medical license, Harley's bedside manner takes over, and she drops down to check on the collapsed girl, asking how badly injured she is as Ivy tells her they don't have time for this. The kidnapper has the stupidity to approach and lie that the girl is his cousin. She begs them for help, considering them the Lesser of Two Evils as he insists that she is a little confused and she says he hit her. That makes Ivy pause. Even though it's not their problem and they're both criminals, the women think Playground is absolutely disgusting and beat the stuffing out of him to save the child. When Batman arrives, he lets the women go while giving Playground an antidote for Ivy's venom, thinking they deserve a pass for this good deed.
In one mystery story, Batman works endlessly to save an inmate from death row, even though all of the evidence points to the criminal committing a murder. With literal minutes before the execution, the Caped Crusader is able to prove that the inmate is innocent (it turns out that the real murderer was the man's wife). In a bit of a Wham Shot, it's revealed that the prisoner the Batman worked so hard to save was the Joker, who deliberately set the entire thing up for years by arranging for the victim's wife to discover his supposed infidelity, just to exploit this trope and force the Dark Knight to save him. The Clown Prince of Crime gloats that the blood of any of his new victims will now be on his foe's hands, but Batman counters that the Joker now owes him his life, and swears that when he does finally bring him down, it will be for a genuine crime.
In the second series, Booster intends to become a serious, hard-working superhero in tribute to Blue Beetle. Then Rip Hunter offers him a chance to protect the time continuum — by maintaining his reputation as a fool, which will protect him from time-traveling enemies. Booster struggles with the decision, but ultimately accepts his place as the greatest hero that history will never know. (Although, in this case, Rip can offer that he will know that Booster is a great hero, and later two Batmen become Booster's Secret Keepers).
Booster Gold was once offered a chance to join the Justice League personally by Superman. Booster Gold turned it down — it wasn't because he didn't want to join the League, but because doing so might cause rifts in the time continuum that would cause unpredictable results, and he simply couldn't risk it. Not just for himself, but for all of the people from his future. Superman accepted Booster's decision, but the League members were clearly impressed with Booster for showing that level of humility and self-sacrifice.
The Flash: The death of Barry Allen in Crisis on Infinite Earths. Not only is it a Heroic Sacrifice, but it takes place without any witnesses or ability to communicate anyone else. (It's true he flashes through time as he dies, but he has no control over that, nor did he know he could do it in advance.)
Batman himself ends up in this position with the Joker in The Dark Knight Returns. They're in an abandoned carnival ride, the Joker has just killed dozens of people after Batman's return has drawn him out of a decades-long catatonic state, and Batman has sworn that he'll never let the Joker take another life and is prepared to kill him. In the end, Batman can't do it and paralyses the Joker by nearly breaking his neck. Laughing at Batman's lack of guts and knowing that no one else in the world will know he didn't do it, Joker finishes the job for him and kills himself.
The ending of the original Doom Patrol series had their nemeses take a small fishing village hostage, demanding the Patrol's deaths in exchange. The Doom Patrol accepted the deal, and died as obscurely as they lived. Until the inevitable Retcon, anyway.
The corresponding episode in Batman: The Brave and the Bold called "The Last Patrol!" had the Patrol do the same thing, their deaths broadcast all over the world by General Zahl. However, he finds the people end up ADMIRING the Patrol for their sacrifice. The General realizes that even in Death, the Doom Patrol defeated him. In memoriam, the island village of fourteen the Patrol died for is renamed "Four Heroes".
In a villainous version that crosses over with The Only One Allowed to Defeat You, The Joker once met Batman and engaged him in a battle — trouble is, the Dark Knight was fresh from another fight and thus completely exhausted. He promptly collapses, and the Joker realizes that he can finally fulfill his dream of killing Batman. But after a few moments, he decides that the victory wouldn't really be "his", because the Caped Crusader wasn't at full capacity — even though no one else is around and the Joker could easily claim that he overpowered his foe. The Clown Prince of Crime thus spares Batman's life, vowing that when he does finally kill him, he'll do it fair and square.
A Secret Six chapter contains a chilling inversion of this and other similar situations. The titular group of Villain Protagonists is hired to snatch a pedophile serial killer from police, by the father of one of the said killer's victims, who intends to avenge his daughter personally. However, when Catman and Deadshot deliver the safely bound killer into an isolated storehouse, where no one will hear any screams, he starts backing down, clearly unprepared to take another's life and saying he doesn't think he can do that. Catman coldly responds with "Yes, you can", and a short but detailed instruction about the most painful ways to flense a human. Judging by the man's immediate reaction, he takes this advice to heart.
Public Enemies (2004): When both heroes confront then-president of the United States, Lex Luthor, over a bounty he placed on Superman's head, blaming Luthor for an incoming meteor (made of Kryptonite or containing it at least) about to hit the earth, and the beating he just gave to their respective proteges, Superman has been pushed so far he is ready to fry Luthor. Luthor actually goads him, believing Superman wouldn't do it or that if he did, the fact that Superman committed murder would be a massive blow against him and the people's faith in him, thus a form of post-mortem vengeance against Superman. However, that is when Batman shows up and quite calmly tells Superman he [Batman] won't stop him, and that they can just make it look like an accident or "better yet, as if he'd vanished without a trace." Luthor begins sweating cold when he realizes he may genuinely lose his life for good. Needless to say, Superman doesn't kill him and settles for throwing him against the wall before leaving to stop the meteor. Which was what Batman probably knew would happen all along. Probably.
In Man of Tomorrow #7, "When No One's Looking", a new hero, Soar, arrives in Metropolis and begins defeating villains while posing for the cameras. Jimmy Olsen even becomes his photographer, despite Superman's misgivings about the man. Then it turns out that Jimmy also suspected something was fishy and by the end of the story, he's tracked down the evidence to prove that Soar brought the villains there to show off by beating them. Soar protests that he had no chance of winning any heroic acclaim without stacking the deck as long as he had to compete with Superman. The young reporter chews Soar out, saying that Superman is a real hero because he does what he does regardless of if anyone is watching.
In The Killers of Krypton, Supergirl fights and defeats Empress Gandelo in uninhabited planet Tavaar. She could have taken revenge for her dead kin and friends by killing Gandelo right there and then, and nobody would probably have found out about it. Instead, she chooses to keep her imprisoned in a rock while she figures out who turn Gandelo over to.
"Supergirl's Big Brother": While trying to stop a crook named Biff from plundering a sunken ship, Supergirl stumbles upon a cache of Kryptonite rocks. Biff is about to abandon her and make off with the gold, thinking happily she will never reveal his real identity to anybody now, but his conscience starts torturing him. Reminding himself that she saved his life not long ago, Biff leaves the gold and gets her away from the Kryptonite.
"Should Auld Acquaintance Be Forgot": Discussed. Deadman, an obscure ghost superhero that can do nothing but possess others, nearly steals an innocent man's Christmas by spending it in his body (those he possesses have no memory of the time he controls them). As he is lamenting how much it sucks that he can't celebrate the holiday without stealing it from someone else and how the nature of the way he operates means he will never be more than a circus performer that died years ago in the eyes of the world, he meets a mysterious woman that can see and hear him. She reminds him that, as long as good is being done, it doesn't matter if the world knows who did it. It doesn't matter if no one remembers you ever even existed at all. Before she leaves, Deadman asks her for her name.
My name is Kara, though I doubt that'll mean anything to you.
The Superman Adventures had a two-part story titled "The War Within" where a doctor tending to Superman when the latter is infected with a deadly Kryptonian virus is blackmailed by Luthor and Mercy Graves to give Superman a poison instead of the actual antidote under penalty of being exposed for a past case of malpractice. Superman tells the doctor that he trusts him, which persuades the doctor to defy Luthor's orders and give Superman the real antidote.
In Watchmen, the protagonists are faced with this after Ozymandias unleashes his master plan to save civilization from nuclear war by wiping out half the population of New York in a staged alien attack, which will force the nations of the world (and especially the U.S. and Russia) to stop the Cold War and work together for a solution. The group is at a loss: the public has a right to the truth about all of the deaths and other illegal activity the plan required, but revealing that truth would also create so much animosity and anger that war would easily break out, just as Ozymandias planned in the first place. They agree to say nothing, but Rorschach won't do it, citing his philosophy—"Never compromise"—as a reason, forcing Dr. Manhattan to kill him to preserve the planet. As with the majority of the book, it's ultimately up to the reader to decide who, if anyone, was right.
Wonder Woman: Warbringer: The Oracle offers to stay quiet and just let Alia die, which would restore the balance in Themiscyria, prevent Diana from facing the consequences of breaking the law by bringing Alia there, and stop the war that Alia is foretold to bring. Diana chooses the difficult path of trying to save Alia, Themiscyria and the world.
