->''Always forbidden, on occasion mandatory.''
-->-- ''Songs of Earth and Power'', Creator/GregBear

How desperate must a situation be for [[GodzillaThreshold a certain action to be acceptable]]?
How heinous [[WhatTheHellHero can a course of action get]] before we decide that the MoralEventHorizon has truly been crossed?

If it wasn't so long, the "Sliding Scale Of Unavoidable Versus Unforgivable" could also have been called the "Sliding Scale Of IDidWhatIHadToDo Versus MoralEventHorizon".

In a SadisticChoice, it can be argued that ''both'' options would be wrong, so unless you find a way to TakeAThirdOption, you will do wrong no matter what you do. Then again, in the same situation, it could be argued that both options are right; that they are ''both'' the "lesser evil", although in different ways. Furthermore, it's not like everyone is ''capable'' of taking a third option, as that sort of thing requires one to be able to think outside of the box, so to speak, and the power to overcome the measures set in place to restrict them to two.

Closely related not only to SlidingScaleOfIdealismVersusCynicism, but also to SlidingScaleOfSillinessVersusSeriousness and MoralDissonance. A highly idealistic plot might very well feature brave heroes who slay countless humans or humanoids, the mass-murder or even [[WouldBeRudeToSayGenocide genocide]] being [[HandWave Hand Waved]] by dismissing the victims as AlwaysChaoticEvil.

Since a PrinciplesZealot and a TotalitarianUtilitarian measure this scale quite differently, they are very likely to mutually accuse ''each other'' of JumpingOffTheSlipperySlope. To some extent, this is even true for their reasonable counterparts, the [[ForHappiness Ethical Hedonist]] and [[ForGreatJustice The Deontologist]].

Of course, the issue of sliding scales and slippery slopes does not only include the active action of actively doing something, it ''also'' includes the passive action of inaction - to choose to do nothing and just let things happen is ''also'' a choice. A choice that you can be held accountable for, just like any other choice.

Also, when the Sliding Scale Of Unavoidable Versus Unforgivable comes up in a story, it can be either intentionally or indirectly. It's intentional when the writers decide to make the situation [[GreyAndGreyMorality ambiguous and debatable]]. It's indirect when the situation is intended to be [[BlackAndWhiteMorality unambiguous]], but the reader/viewer goes [[ValuesDissonance "waaait a minute"]]. However, one can never really be sure what version was the intended one, considering that WordOfGod is vulnerable to GettingCrapPastTheRadar as well as blatant {{RetCon}}s.


[[folder:Anime & Manga]]
* ''Anime/CodeGeass'' is all over the place with this one. In fact, it seems it's the main question the show poses: how far can you escalate to achieve your goal, however noble it was, before you [[HeelRealization stop being you]]?
* ''Franchise/SailorMoon'' pretends to raise this question a few times, especially with the Outer Senshi (particularly Uranus and Neptune), who are less sold on ThePowerOfFriendship and more willing to resort to more extreme, [[GoodIsNotNice destructive]] tactics than the Guardian Senshi. If the team decides to go the "nice" route, though, it turns out that whatever awful thing was supposed to happen doesn't happen [[spoiler:like, Sailor Saturn's birth doesn't result in the apocalypse!]] Or [[TakeAThirdOption a third option]] arises. Or, if they go the [[FakeDefector mean route]], [[HoistByHisOwnPetard it backfires]]. Also, anyone who makes a HeroicSacrifice [[BackFromTheDead gets better]]. Point is, ''Sailor Moon'' ultimately comes down on the Unforgivable side, with a convenient DeusExMachina there to make sure that the "nice" choice always turns out to be the best.
** Except that ''quite'' a bit about [[spoiler: Saturn]] is implied through a blink-and-miss-it scene in the [[Anime/SailorMoon anime]] ([[spoiler:Pluto being depicted as a gas giant in a [=SilMil=] flashback]]), and ''her own actions'' in the [[Manga/SailorMoon manga]] ([[spoiler: donning a [[DissonantSerenity playfully]] [[PsychoticSmirk predatory smile]] while killing [[EldritchAbomination Pharaoh 90]] and his multitudes of spawn more slowly than strictly necessary]]). And in ''both'' incarnations of the series, you have to wonder: just why ''is'' the asteroid belt so much younger than the rest of the solar system? Throw in the fact that in the manga, the talismans were for waking her up (making her a PersonOfMassDestruction that requires ''three keys'' to activate (for reference, modern nuclear devices only require two)), and you start to think that perhaps, in the [=SilMil=] at least, the Outers' caution would have been ''more'' than warranted. Almost like, if she activates, a few billion somethings are ''going'' to die, and she doesn't particularly care ''what'' those somethings are.
* Most of the subtext in the ''{{Manga/Trigun}}'' manga and a lot of the overt text is about this. Anime a good deal as well. [[AntiHero Wolfwood]] is the avatar of IDidWhatIHadToDo; one of his catchphrases is the 'not to choose is also a choice' line mentioned above. [[MessianicArchetype Vash]] is determined to be a WideEyedIdealist hardliner in the face of a CrapsackWorld and save everyone. [[BigBad Knives]], meanwhile, falls somewhere between taking Wolfwood's approach to horrifying extremes and just being a megalomaniac.
** Interestingly, Knives is generally saner and more rational in the anime and engages in less actual evil because most of the plot got carved out, but his reasons for deciding to KillAllHumans are by comparison spurious.
*** Legato, meanwhile, who's the fourth major psyche vivisected, doesn't operate in a universe where right and wrong are particularly meaningful concepts, especially not as guidelines for his own behavior. Although anime!Legato does invoke the idea that he and everyone else (except [[MadLove Knives]]) are awful, egotistical beings who don't deserve life.
** [[spoiler: Vash wins, but only because he came up with a use of his mostly-dormant psychic powers that reminded all the plants Knives was using to end the world of ThePowerOfFriendship vis a vis the human race and convinced them to spontaneously dessert.]] The anime ending is more ambiguous, which is odd when it's generally less willing to grapple with difficult issues head-on. Though this is less head-on than extremely obliquely.
* ''LightNovel/AiNoKusabi'' brushes the issue at the very end concerning how both of Riki's love interests handle the conflict over him. Iason is portrayed as more sympathetic despite having been a selfish VillainProtagonist and AntiVillain during whole story due to his late positive actions. Meanwhile, Guy ended up becoming a WellIntentionedExtremist FallenHero and possibly a TragicVillain that made things go FromBadToWorse. His actions were avoidable but are they forgivable? Did he cross the MoralEventHorizon when he was determined to "save" Riki?

[[folder:Films -- Animated]]
* ''WesternAnimation/TitanAE'' gets a happy cheerful ending, with the wonderful happy-for-everyone GENOCIDE and [[PoweredByAForsakenChild recycling]] of the antagonist civilization. The dissonance felt by parts of the audience may or may not be intentional, but is there in either case. However, the antagonist civilization was genocidal itself and blew up the Earth in the first place. In the novelization, it's revealed that the Drej annihilated Earth simply because humanity was reaching a [[TechnologyLevels level of technology]] where they could potentially challenge the Drej's supremacy. Emphasis on ''reaching'' and ''potentially'', which, of course, makes the destruction of the Drej more of a KarmicDeath.

[[folder:Films -- Live-Action]]
* ''Film/{{Watchmen}}'' debates this trope. Is [[spoiler:Ozymandias's plan necessary enough to justify the mass murder of millions]]? Rorschach knows his answer, and the others, though horrified, all seem ready to make the pragmatic choice given the state of things. Doc Manhattan doesn't weigh in except to possibly dismiss the concept of the ends justifying the means (since there is no real "end"). "In the end" it's left for the audience to decide.
* This is pretty much the point of the ''Vengeance Trilogy'' (''Film/SympathyForMrVengeance'', ''Film/{{Oldboy|2003}}'', and ''Film/SympathyForLadyVengeance''), where you're meant to feel sympathy for the antagonists and question the deservedness of the protagonists' revenge, while both cross seemingly many a MoralEventHorizon in order to pursue their goals, only for it to just about excuse everyone based on what they've been put through by each other...
** ...well, apart from in [[spoiler:''Film/SympathyForLadyVengeance'']], where the antagonist is never presented as anything but evil, but the deservedness of the protagonist's revenge is still called into question by the end.
* ''Film/AustinPowers'' deconstructs this with heavy MoodDissonance scenes of AlasPoorVillain: When the heroes kill a PunchClockVillain in a funny way, the scene is suddenly cut to the victim's grieving family and friends.
** Those scenes were cut in the American release, likely to avoid stated MoodDissonance.
* In ''Film/TheBourneLegacy'', Byer states that the actions of Outcome agents (and likely those like them) are "Morally indefensible, and absolutely necessary". He [[JumpingOffTheSlipperySlope jumps off the slippery slope]] when he takes part in the cover-up when Outcome and several other such operations start having their mission corrupted by sinister powers in the US intel community and then gets exposed by more morally upright powers.
* ''Film/ExMachina'' AVA's decision to [[spoiler: leave her would-be rescuer, Caleb, to die]] was thought to be necessary by the writer/director and unnecessary by pretty much everyone else.

* Halfway through ''Literature/HarryPotter'', Harry (and the reader) learns of Unforgivable Curses - [[MindControl Imperius]], [[AgonyBeam Cruciatus]], and [[InstantDeathBullet The Killing Curse]] - which are (as the name says) Unforgivable, and carry a mandatory life sentence in Azkaban if used. Cut to book 7: Harry, Hermione and Ron use the Imperius curse as part of an infiltration mission, and even the [[AgonyBeam Cruciatus curse]] once or twice. Hell, ''Professor [=McGonagall=]'' uses Imperio at one point! It's a clear evocation of the inevitable moral progression war inflicts upon even the so-called "good guys".
** This isn't even touching on the [[InstantDeathBullet Killing Curse]], the third of the Unforgivable Curses. Of course, the use of ''that'' one would be justified in any situation where shooting to kill is a necessity (though wizards, with the specific nature of their spells, would find it more feasible to aim for mere incapacitation than a man with a gun would,) but Lord Voldemort and his cronies using it as their signature spell wasn't really good for its PR. Or, you know, the fact that its entire existence is for killing, since it can't be used to threaten or incapacitate even as much as a gun can.
*** That may be due to the fact that it - supposedly - can not be countered by any known spell and there's no way to defend yourself against it. [[InformedAbility Or so they claimed.]] Apparently there were a few (okay, more than a few) ways to defend yourself from it that no-one knew about...
** As Harry learned in fourth year Defense Against the Dark Arts and from Bellatrix [[spoiler:when he tried to use Cruciatus on her]] in ''[[Literature/HarryPotterAndTheOrderOfThePhoenix Order of the Phoenix]]'', in order to successfully pull off an Unforgivable Curse, you have to really, truly, '''mean''' it. The implication is that The Killing Curse requires intense vitriol, true hatred for the target (or towards one's own actions, as may have been the case with [[spoiler:Snape]]). The spell is explicitly MURDER, not self-defense.
** The alternate explanation is that the requirement for strong intent is simply a magical failsafe against accidental use. It isn't necessarily a requirement to ''hate'' the target; hatred just makes the level of intent easier to achieve.
** It's Voldemort's own fault that the heroes were free to use Unforgivables in ''[[Literature/HarryPotterAndTheDeathlyHallows Deathly Hallows]]'', as the Ministry under his command [[http://harrypotter.wikia.com/wiki/Unforgivable_Curses#Use legalised them]] with the intention of using them against his enemies. [[HoistByHisOwnPetard Isn't karma wonderful?]]
* ThreeWorldsCollide and its ''extremely'' ShootTheDog "True Ending", which inspired plenty of debate in the comments.
* In Literature/TheDresdenFiles, Harry[[spoiler:'s subconscious]] makes this argument, pointing out that if [[spoiler: Harry]] takes the high road in Dead Beat, thousands of people will die.
** [[spoiler: Lasciel]] tries very hard to make you believe that the decisions you make are unavoidable. At one point [[spoiler: Harry]] went nuts on a mook and might have been able to save an injured Muggle if he'd let that mook run. This was before he knew that [[spoiler: Lasciel was in his head, making him act towards the unforgivable end of the spectrum, while assuring him that it was just an unavoidable situation]].
** Harry has a minor one of these, with shades of MyGodWhatHaveIDone, when he realizes how many antagonists have ended up dead in his cases. Bonus points for that being from a ''mobster''.
** [[spoiler: Molly]] toys with this line a lot, including using forbidden mind magic.
** Harry's mother was known for pointing out the gray areas in this scale that she felt weren't adequately covered by the Laws of Magic, or were covered too harshly.
** [[spoiler: Harry]] eventually crosses this line wholesale in one of the later books [[spoiler: by finally becoming the Winter Knight]]. Though he believes it was unavoidable, in the next book he gets convinced that it was unforgivable, based on the decisions that [[spoiler:Molly made in response]].
** Harry frequently points out to whichever MonsterOfTheWeek that's trying to recruit him that while they're touting the unavoidable end of the spectrum, he knows that they'll push him to the unforgivable end pretty quickly.
** [[spoiler: Ghost Story]] turns out to be a massive BatmanGambit to teach Harry that it's possible to avert this trope.
* In ''Literature/ASeriesOfUnfortunateEvents'', this question comes up in Books 10 and 12. Interestingly, the actions discussed in book 10 ([[spoiler:ambush and kidnapping to exchange hostages]]) are decided to be unforgivable, but by the twelfth book things have become so dire that their actions ([[spoiler:arming children with deadly weapons and arson among them]]), while arguably worse, are implied to be unavoidable. It helps that they were trying to stop a villain from using a DepopulationBomb in the middle of the only major city mentioned in the series.
* The Queen of Attolia from ''Literature/TheQueensThief'' series. She's ruthless, has a habit of hanging criminals upside-down from her castle walls, tortures prisoners and [[BigBrotherIsWatching spies on her own spies]]. But if she wants to be a female ruler in a sexist society, keep her rebellious barons in line, and hold off the Medean Empire, she ''has'' to be terrifying and ruthless.

* ''Series/StarTrekDeepSpaceNine'': This is what made "In The Pale Moonlight" one of the darkest episodes in ''Franchise/StarTrek'' history. The casualty list in the war against the Dominion gets so bad, that Sisko feels he has no choice but to go against his Federation principles to trick the Romulans with a fake offensive against them in order to get their support. And when the trick is found out by the Romulan sent to verify the information, [[spoiler:Garak sets up their ship to explode, and when the Romulans search the ship, they will find the fake info and come to the conclusion that the data corruption of the info was due to the explosion.]] In the end, Sisko decides that having the stain on his conscience is worth having fewer lives lost.
* ''Series/StarTrekTheOriginalSeries'': In "A City on the Edge of Forever", Kirk had to make a terrible choice -- [[spoiler:allow a wonderfully gifted, compassionate, forward-thinking woman to die, or fail to save history from devolving into a CrapsackWorld.]] Kirk rather uncharacteristically didn't TakeAThirdOption, such as, say, trusting her with the truth.
* ''Series/DoctorWho'': Seeing the number of times you can make the Doctor contemplate this scale is the pastime of the show's writers, especially since the reboot. The Doctor had to kill (technically, 'erase from continuity') his entire race in order to protect the universe from destruction, and even though he knows it was the right thing to do, he still feels guilt-ridden. Time and time again, he is forced to make the SadisticChoice of killing and committing genocide for the greater good. On the whole, the show tends to fall on the IDidWhatIHadToDo side, although the fact that the Doctor is ''capable'' of such decisions is still depicted as terrifying.
* ''Series/{{Torchwood}}'' pulls it now and then too, but especially in ''Children of Earth'', where Jack Harkness sacrifices his own grandson in order to prevent a tenth of all the world's children from being sold into perpetual slavery for an alien race that wants to use their body chemicals as recreational drugs. Throws the whole WouldntHurtAChild thing up for inspection. And WordOfGod says he couldn't even have done that had his MoralityChain not bitten the dust in the previous episode.
* ''Series/BuffyTheVampireSlayer'' provides us with three in the fifth season finale. First, Ben is convinced that he has no choice, and can either fail to fight a god or earn that god's favor. Second, Giles [[spoiler:kills Ben]], saying he had to do it because, unlike Buffy, he's not a hero. Then Buffy faces what she's been trying to prevent, whether to kill Dawn or let the world suffer hell. In the end, she opts to [[spoiler:TakeAThirdOption]]. In a later season, Buffy admits she would have killed Dawn to save the world.
* This Trope is more or less the entire point of ''Series/BreakingBad,'' and the plot could be condensed down to Walter White slowly moving from one side of the scale to the other. In the beginning of the series he starts cooking methamphetamine to leave his family a large inheritance and pay for his cancer treatments, but as the series progresses he commits more and more heinous acts with less and less justifiability. People may disagree on what his MoralEventHorizon was, and at what point he turned into an outright VillainProtagonist, but there's no doubt he had one and by the end of the series that's what he is.

* A very common, indeed cliched, element to appear in ''TabletopGame/DungeonsAndDragons'' for its first three (and a half?) editions when game-masters dealt with the Paladin class. That class paid for divine grace and dispensation with a strict code, which far too many Dungeon Masters regarded as a requirement for absolute perfection. All too often, attempts to introduce 'moral quandaries' would take the form of problems that could only be resolved by violating the code. Unlike literature and film, the ability to TakeAThirdOption was not always available (or, in the case of particularly poor Dungeon Masters, permitted.) This has led to many, many 'recreational' hours being wasted in disgruntled debates. More recent editions of the game hold the Paladin to less arduous standards and de-emphasize the referee's ability to remove the Paladin's powers.
* A large portion of the setting of ''TabletopGame/Warhammer40000'' manages to be at both extremes simultaneously.

* The DrivingQuestion of ''VideoGame/HeavyRain'': "How far would you go for someone you love?" In short, would you commit increasingly immoral acts if they offered a slight chance of saving your child?
* ''VideoGame/{{inFamous}}'' has one choice at a certain point where [[spoiler:Trish]] is hanging from one side of a building and several doctors from another. The evil choice is to not save the doctors, but it really comes down to the lesser evil rather than a choice that's outright wrong, and you aren't allowed a third option. No matter what your choice is, however, [[{{ButThouMust}} the result is always the same.]]
** ''VideoGame/{{inFAMOUS 2}}'' takes it even further. The final choice in the game is [[spoiler:a choice between killing billions of people to save millions - including the main character and his friends - or killing millions to save billions, and effectively committing suicide in the process. It really comes down to a choice between two evils, where the "Good" choice is really just the lesser one.]] In contrast to the first game, whichever you chose has a very large effect on the game, [[spoiler:determining what kind of final boss you fight and what kind of ending you get.]]
* ''VideoGame/MassEffect2'' has a very unique case of the series in the Arrival [[DownloadableContent DLC]]. In this mission, Shepard is [[spoiler: forced to blow up a Mass Relay and subsequently destroy an entire star system containing 300,000 Batarians, in order to delay the immanent Reaper invasion which otherwise would have been ''immediate''.]] What makes this unique is that [[spoiler: [[ButThouMust the player has no choice in the matter]], which is a huge subversion for the series. The fact Shepard is ''forced'' to blow up the Relay only highlights the desperation of the situation; and for once, [[TakeAThirdOption there is no third option]].]]
* VideoGame/MassEffect3 gives us two situations where this trope is in play. The first is deciding whether or not to cure the [[ExplosiveBreeder Krogan]] [[DepopulationBomb genophage]]. Do you cure the genophage to gain sufficient military assets to defeat the reapers, but risk a new [[BloodKnight Krogan]] [[ZergRush rebellion]] when the galaxy is militarily weak? Or do you sabotage the genophage, trick the Krogan into supporting you, but doom them to genocide?
** Then there is the question of how to deal with the Reapers? Do you KillEmAll but in the process doom every [[ArtificialIntelligence synthetic life form]] in the galaxy? Including your trusted friend EDI, who might have even learned to love? Or do you reprogram the Reapers to obey a new controlling intelligence based on your own thoughts, but [[HeroicSacrifice die in the process]] and possibly consign the Galaxy to live under an oppressive rule forever? Or do you choose to pacify the Reapers and invalidate their PretextForWar by inflicting [[CyberneticsWillEatYourSoul cybernetic augmentation of every living creature's DNA without its consent?]] And bring into sentience [[WasOnceAMan cybernetic]] [[BodyHorror monstrosities created by the Reapers to terrorize and subjugate populations.]] And allow the Reapers to [[KarmaHoudini get off scot-free on about twenty thousand instances of galactic genocide?]] Which of these is an acceptable trade off?
* ''VideoGame/{{Warcraft}} 3'' has several examples of this in campaign mode, one of the reasons it's considered a very engaging plot. Possibly the most famous example is the Culling of Stratholme: the heroes come on a city that's already infected by TheVirus, and the party splits over the decision of whether to purge the city before the citizens can turn into zombies.
* ''VideoGame/DarkSouls'': ''VERY'' vaguely played with in various {{NPC}}s (Gwyndolin's schemes and Solaire's outcomes, for instance), but most of all in [[MultipleEndings the endings]]. [[AmbiguousSituation There's a dichotomy alright, and either could fit the "unavoidable" or "unforgivable" labels depending on how you interpret the events of the main game]]. Still, unless there was a "third option" the player was never given in-game, then one ending ''was'' indeed less bad. [[RiddleForTheAges Whichever that was]].
* The player's response to the ending of ''VideoGame/DragonAgeII'' will largely depend on where they would place [[spoiler:Anders]] on this scale after his actions at the end of Act 3. The question of whether his crime of [[spoiler:blowing up the Kirkwall Chantry and murdering Grand Cleric Elthina in the process]] was Unavoidable or Unforgivable is one that has split the fandom: some believe that it was unavoidable due to [[spoiler:Anders having spent years pursuing a peaceful means of gaining mage rights and not getting anywhere with it, and with drastic action being the only course left open to him]]; meanwhile, others feel that it was unforgivable because [[spoiler:the explosion killed many innocents, and was one of the primary events that sparked the Mage-Templar War, a conflict that would cause many more deaths]]. The player can respond to this by [[spoiler:killing him, telling him to leave, asking him to come with you and make up for what he did by aiding you in the ensuing fight (although this requires 100% Rivalry should you side with the Templars), or, if romanced, by running off into the sunset with him as a fellow fugitive]], effectively giving the player the choice of where he canonically falls on the scale.
* ''VideoGame/AVeryLongRopeToTheTopOfTheSky'': [[spoiler:Raccoon]] goes through a lot of Angst over this, not that it stops him in the end.

* ''{{Webcomic/Homestuck}}'' has Vriska, who [[{{Jerkass}} revels]] in making [[IDidWhatIHadToDo these sorts of decisions]]. [[spoiler: Breaking Stable Time Loops results in dooming everyone in that timeline. On one occasion, Vriska decides to create a major villain that threatens the lives of her friends in fulfillment of a stable time loop.]]
** She later decides to seek out an ultimate weapon to defeat a villain, which is apparently only obtainable by forcing others to be {{Cannon Fodder}}.
* The ''Kings War'' arc of the MassiveMultiplayerCrossover ''{{Webcomic/Roommates}}'' deals with this trope heavily, while pitting [[GoodVersusGood two good characters against each other]]. One is an ex HeroAntagonist [[spoiler:James Norrington]] from a story with plenty of grays (he is the "Unforgivable" side, for simply knowing of the gravity of killing/waging war/etc.) the other is a BigGood [[spoiler:Glinda]] from one perfectly black and white children's tale (she is the "Unavoidable" side because, well, [[BlackAndWhiteInsanity black and white has a problem comprehending gray]]).

* Wiki/SCPFoundation: [[http://scp-wiki.wikidot.com/scp-231 Procedure 110-Montauk]].

* ''WesternAnimation/AvatarTheLastAirbender'':
** The season 2 opener spends time talking about this. Aang has always been a MartialPacifist, but now that his SuperMode is a known factor, people are encouraging him to go visit the Fire Nation capitol and go all Godzilla on it for the sake of ending the war, and he can't decide what to do. Naturally, it turns out to be more complicated.
** Also notable that in the finale ''immediately previous'' to this season, Aang wiped out a large Fire fleet while in the [[SuperMode Avatar State]] and fused with [[DidWeJustHaveTeaWithCthulhu the Ocean Spirit]]. Casualty estimates are [[WhatDoYouMeanItsForKids of course]] not provided in the work, and fan guesses tend to range from the dozens to the thousands. Aang tends to be given a moral pass on that one, since he was pretty obviously not in control of his own actions at the time (the Ocean spirit continued the rampage even after Aang separated from it), and even then, the Fire Nation were enemy combatants and the aggressors on top of that.
** Played with by Zuko in the last season, in which he tries to justify turning against Aang and his uncle Iroh in the Season 2 finale as "what [he] had to do" to the imprisoned Iroh. Iroh just turns away in silence, and it becomes obvious that Zuko is really trying to convince himself.
** Brought up once again in the series finale, with the interesting twist that Aang's definition of Unforgivable -- taking even a single human life -- is in sharp contrast to everyone else's, who all agree that the Fire Lord needs to be killed. [[spoiler: Even Ozai's son and brother and ''all'' of Aang's past lives agree!]] Aang's desperate search for another option drives the plot for the first hour or so.

* The entire concept of Total War invokes this trope. What is typically unforgivable (most specifically, targeting civilian targets) becomes unavoidable because the entire country is thrown into the fight.
* The use of saturation firebombing (an Allied tactic) and V-2 rockets (on the Axis side) during World War II. When war materiel production was decentralized (and small workshops in civilian centers used to produce weapons and ammunition), attempts to restrict themselves to strictly military targets were abandoned. Tokyo and Dresden were virtually annihilated. Tokyo is particularly notable - it killed more civilians than ''either'' one of the atomic attacks... speaking of which:
* The [[UsefulNotes/NuclearWeapons atomic bombings]] at Hiroshima and Nagasaki. On the one hand, it ended the war in '''very''' short order, likely saving lives on all sides. On the other hand, they were still deliberate nuclear strikes on ''civilian cities,'' with heavy residential zones within the radius of guaranteed destruction.
** Whether or not it was truly unavoidable is still hotly debated. Historical arguments on this point should go elsewhere. The key point here is that as far as Truman (who was not privy to internal Japanese politics) knew, the only choices were the nuke or an invasion of the Japanese homelands. An invasion would have been even more bloody and costly for both sides, as the Japanese instructed its people to either kill any American soldiers, or commit suicide.
** Another consideration was that, had the war not been ended with nuclear bombs, America's WW2 allies/soon to be the new BigBad, the SovietUnion, were believed to be planning to invade Japan from the north. Had Japan been conquered that way, the likely result would have been a Communist North Japan and a Pro-Western South Japan, as happened with Korea and Vietnam. One can obviously debate whether or not this makes the use of the nuclear bombs more acceptable.