Let's Fight Like Gentlemen



"Fezzik: We face each other as God intended. Sportsmanlike. No tricks, no weapons, skill against skill alone.

Man in Black: You mean, you'll put down your rock and I'll put down my sword, and we'll try and kill each other like civilized people?"

- The Princess Bride

So, let's look at what the situation has turned into: the Hero stands across the battlefield from the opponent, be it in the form of a Big Bad, Arch Enemy, Lancer, Evil Counterpart, a Gentleman Thief, Rival (with or without a heel turn), you name it. It is abundantly clear from the story arc building up to this climactic battle that neither side will rest until the other is face down in a puddle of their own humiliation. Chances are they will pull out all the stops, and resort to some of the dirtiest and underhanded tactics conceivable, right?

Well, yes and no...

See, both parties understand that there are certain rules, unwritten or otherwise, that dictate how a battle can be waged. And they plan to see that they are upheld. Sure, this is an intense rivalry that must be settled once and for all, or possibly the fate of the world hangs in the balance, but there's no reason why we can't be civil about it! We're not barbarians (and said barbarians who circumvent the rules get beaten/dressed down by both the hero and his opponent; literal barbarians often follow this trope themselves)! Ultimately, it could be because the villain wants to maintain an air of dignity even in defeat, or maybe he just wants to show The Hero that he can beat him at his own game. It could also be that the two parties simply want to see it done right, so that there can be no squabbling about what could have been (even the playing field and settle this once and for all).

Formally staged battles, like Combat By Champion, Duel to The Death, or Gladiator Games, may require it; you may lose if you cheat.

There is some overlap with The Only One Allowed to Defeat You. A villain who sees The Hero as a Worthy Opponent might invoke this Trope as well. One of the standard codes by which Cultured Badasses operate. Contrast with the Combat Pragmatist, who only fights by the rules when it's to his benefit to do so. Has overlap with Combat Aestheticist.

Anime and Manga

 * Every Yu-Gi-Oh antagonist fits the bill in one form or another, from Seto Kaiba to Pegasus to Malik Ishtar to Dartz. They might cheat at the game, but they still "fight" the heroes through Duel Monsters instead of by actual force. Pretty much any series that revolves around a game of some kind will fall under that description, but it still fits. Pegasus is the most prominent example of this.
 * In Yu Yu Hakusho, Yusuke and Chu eventually agree to settle their fight with a specific kind of knife fighting, forgetting entirely about the rules of the Dark Tournament itself (i.e., by actually having rules).
 * Most professional assassins wish to usurp the City Hunter at the top of the assassin food chain. So when such professional assassins do run into him, there is an agreement on how the fight will start, and an agreement on how the fight will end, either by death for the loser, or the loser permanently leaving town and having his/her reputation permanently stained (which apparently is far worse in the assassin world).
 * During the Cell Saga of DragonBall Z, Cell plans on destroying the world! ...unless he can be defeated in a tournament, fair and square. He even sets boundaries, just like in the Tenkaichi Budokai, so there's a chance a powerful super-being like him could lose by ring-out.  However, it's worth noting that Cell only plans on following the rules until the moment arises that he realizes he could actually lose, at which point he starts cheating rather than face defeat.
 * In Mobile Fighter G Gundam, the rules specifically state that all fights should be one-on-one. In the third episode, Domon stops a match from starting; when one of the fighters chews him out for breaking the rules, Domon calmly takes out the other fighter with a single attack and then remarks that the fight hadn't formally started so it wasn't a violation.
 * Mobile Suit Gundam Wing
 * Wufei first fights Treize in a Sword Fight, although he could've just as easily used his Gundam to destroy Treize's ship. Treize easily beats him, then allows him to leave. Wufei suffers a Heroic BSOD for a couple of episodes after this.
 * A few episodes later, Zechs fakes destroying the Wing Gundam, rebuilds it in secret, AND tracks Heero down (protecting him from OZ hit squads at the same time), all for a fair fight. Even moreso, he has his mechanics undo the repairs to his Humongous Mecha's left arm precisely because it was damaged in the fight that OZ interrupted and he wanted to re-create the exact circumstances of that fight. Heero partially subverts this trope by refusing to use the rebuilt Wing, insisting that Zechs' charity would cloud his feelings and make him hold back, defeating the purpose of a "fair fight."
 * In Asu no Yoichi, Yoichi will often gladly fight those who challenge him to a fight, and will often fight with whatever their opponent is using. So if it's a fistfight, he won't use his sword. However, if they fight him for less than pure motives, such as being paid to defeat him, then he pulls a Warrior Poet moment on them and then does a Curb Stomp Battle on them.
 * In High School DXD, Sairaorg Bael will fight the protagonists team in a Rating Game only if they're at full power; lifting the ban of their Power Limiter in their match.

Film
""Martial art is based on deception, my friend.""
 * In one memorable scene from the movie Hitman, Agent 47 gets into a gunfight with 3 other assassins in a subway station. But after a call to "die with dignity", all the assassins drop their guns, pull out two swords secretly hidden on their backs, and proceed to have a swordfight.
 * Subverted in Back To The Future Part III in Marty's showdown with "Mad Dog" Tannen. Marty discards his gun, saying he "thought we could settle this like men".
 * Subverted in the movie The Forbidden Kingdom, when the Jade Warlord challenges the Monkey King to a fair fight without his magic powers or the Monkey King's magic staff. However, the minute he puts aside his staff, the Warlord uses his magic to turn him into a statue.

"Operative: [Gets back up] I am, however, wearing full body armor. I am not a moron!"
 * When confronted by Bart at the end of Blazing Saddles, villain Hedley Lamarr claims to be unarmed. Bart puts aside his gun for a fistfight. Hedley was lying. Hedley ends up getting shot anyway.
 * The Patriot. General Cornwallis upholds this method of conducting war to the highest degree. His subordinate, Col. Tavington...not so much.
 * Which was based on the real-life figure of Colonel Tarleton. His tactics were known for their brutality and harshness yet when he got back from the Revolution to England (unlike the movie he does survive) he was the toast of the Empire as the greatest hero to emerge from the war.
 * Wasn't there a scene where Cornwallis was trying to justify soldiers attacking civilians? That's not a proper way to wage war. His justification was that things happen during wars, but that goes against his earlier comment where he insists Tavongton behave like a gentleman during battles.
 * Subverted Trope in A Fish Called Wanda, when Otto implies that Archie is not manly enough to face him without a gun. Archie puts down his gun, declaring "I used to box for Oxford!" "I used to kill people for the CIA," Otto replies, picking up the gun and threatening Archie with it.
 * The Princess Bride has two of these. Fezzik is one, as indicated in the page quote; the other is Inigo Montoya, who, although just waiting for the Man in Black to finish climbing the Cliffs of Insanity so he can duel him to the death, very pleasantly assists him in reaching the top and allows his opponent to get his breath back and remove some rocks from his boots before undertaking the fight. He even provides background exposition about why he's in the villain industry while he waits.
 * And hands his sword to the Man in Black so that he can marvel at the craftsmanship, leaving himself completely defenseless. The Man in Black compliments him then gives the sword back.
 * And on top of that, they compliment and discuss each other's sword fighting techniques while they're fighting.
 * Lampshaded twice in Serenity. In one scene, the Operative points out that he has come alone and unarmed in order to show that he's serious about settling something with peaceful negotiation. Mal--being Mal--plugs him in the chest. Near the end of the film, the Operative returns the favor by shooting Mal without warning, causing Mal to yell, "You shot me in the back!"
 * Of course, the Operative is far from being Too Dumb to Live:


 * All fights between immortals in Highlander are governed by certain rules. They must be one-on-one and may not take place on holy ground.
 * Of course, plenty of villains find loopholes. For example, in the series, there's an immortal kid who never fights duels, as he's understandably weaker than adults. Instead, he pretents to be a new immortal and a scared kid. Then he sneaks up on his target and lops his or her head off. Apparently, he's got enough strength to lift a sword and cut through a spine.
 * Then there's the villain in Highlander Endgame breaks the first rule and just kills a bunch of immortals while they're tied up and sends his immortal Mooks to prepare a target for him. He then.

Literature

 * Seen quite a bit in the canon Battle Tech universe, where settling disputes with fights between relatively few men and women in their Humongous Mecha is quite common and individual notions of the rules of engagement can shape entire battles. An excellent example may be the final fight in the novel Ideal War (which, despite the name, has up to then dealt mostly with dirty guerrilla warfare and its dehumanizing effects on people): The defenders are positioned in the capital city and it would take a lot of effort and collateral damage to root them out. Faced with that prospect in the pre-battle negotiations, their commanding officer instead decides to do the honorable thing and face their attackers (a unit actually created to embody the ideals of chivalry and commanded by the planetary ruler's liege lord to boot) out in the open to settle things once and for all.
 * This mostly depends on the houses or clans that are fighting and how much they hate each other. Most battles take the form of duels because battlemechs are expensive, even more expensive and in fact nearly irreplaceable are FTL capable drop ships.. In the end it just works better most of the time to have a smaller battle and agree to abide by the outcome, It leaves your force intact to come back later, and you resources intact to be be taken back if/when you return. Notable exceptions are the destruction of smoke jaguar, which was an all out war of annihilation, and the battle of tukayyid which itself was basically a duel on a much grander scale.
 * Generally subverted in the Mercenaries series of games; not surprisingly, the concept of fighting for money does not lend itself well to gentlemanly ways. The subversion rarely lasts for long, however, since at a certain point in the game the main character always ends up picking a side and fighting for them out of a variety of morally noble reasons.
 * Sparhawk and Martel's final duel in The Elenium takes this form. As both men are knights, and old former friends who have literally waited about a decade to face each other in combat, they fight in the honorable fashion, and allow each other a short breather when they grow tired, talking and assessing each other's styles while they rest before returning to trying to kill each other. For extra points, Martel suspects he's going to lose anyways, and knows he's going to die several attacks before the final blow falls because of his mastery of swordplay.
 * In Chris Roberson's Warhammer 40000 Imperial Fists novel Sons of Dorn, Jean-Robur is warned that the enemy do not fight properly. In his first battle, he quickly learns to play Combat Pragmatist.
 * In Matt Farrer's "After Desh'ea" (in the Horus Heresy book Tales of Heresy), Angron is spitting with fury because the War Hounds will not fight him properly, giving him their names and all the rituals of the Gladiator Games.
 * The code duello in Honor Harrington, enforced by the fact that the line judges shoot you if you cheat. This happens to Pavel Young in his fight against Honor. After trying to avoid being challenged by her (he saw the Curb Stomp Battle she gave the professional in his employ), he's stuck meeting he on the field. He tries to shoot early, and gets blown away. Not that he had a prayer in the first place. A Karmic Death if ever there was one.
 * Used repeatedly in the Chronicles of Narnia series. King Miraz in Prince Caspian, for example, is goaded into a duel by his treacherous underlings despite being in a position where his army should be victorious without effort. He fights High King Peter and for all his faults, certainly doesn't lack for courage nor does he attempt to cheat in the duel.
 * Eustace, a thoroughly unlikable nerd from England mid-20th century, finds himself unwillingly transported to Narnia, he is dumped into the ocean and rescued by what amounts to a medieval sailing ship. He's naturally not happy about it, but acts like a thoroughly unlikeable Jerkass to make sure he doesn't gain sympathy as the Only Sane Man. Later, he pranks a roughly two foot tall talking mouse named Reepicheep by yanking his tail. Reepicheep responds by attacking Eustace with his sword and demanding a duel to the death. Eustace has to be educated by the other characters about just how serious this is and they consider handicapping Eustace since he's so much bigger than Reepicheep. Now, Reepicheep may have legitimate reasons to be furious with Eustace, but all the other characters believe (and the author clearly expects the reader to agree) that the best resolution to this conflict is somebody should die and Eustace's sulky apology is a cowardly way out.

Live Action Television
"Deirdre: We agreed no weapons!
 * Subverted in The Mystic Knights of Tir Na Nog. One of these fights is going on when the Big Bad Maeve tosses The Dragon a sword:

Maeve: We also agreed no rules."


 * In one of the best Dream Sequences in Gilligans Island, Lord Admiral Gilligan refuses to fight his pirate foes unfairly and tosses them swords with a "Ho," [tosses a sword to a pirate], "Ho," [tosses a sword to a pirate], "Ho," [tosses a sword to a pirate] "Ho," [tosses his own sword in the general direction] "Oooh..."

Professional Wrestling

 * Professional Wrestling. Even if you steal another man's love interest, wreck his material possessions, try to kill him, or light him on fire, the only proper retribution is to get the offender in that very ring and pin his shoulders to the mat for a three-count.
 * It's not always that way: sometimes you have to make him bleed or say "I Quit" instead.
 * And really, it's subverted half the time. Most recently, there's been Shawn Michaels/Chris Jericho round two, with both men doing all kinds of bodily harm to each other in a high-profile Unsanctioned Match.
 * An especially gratifying subversion came in that match when Jericho had Michaels in the Walls of Jericho, his signature submission hold. Michaels fought for the ropes and finally grabbed them, which in a normal wrestling match would mean that Jericho would have to break the hold. Usually, even in hardcore matches where people smash each other up with weapon after weapon and disqualification isn't even a possibility, the wrestlers still abide by rope breaks for some infuriating reason. However, here... Jericho just didn't release the hold. That is, until Michaels grabbed a fire extinguisher from under the ring and decked him with it.
 * Because the way the kayfabe rulebook is set up a ref can't count a pin or accept a submission when a guy is holding the ropes. So the match can't end.
 * More often then not, it is subverted with the idea that the two rivals will fight again, this time in a match where their method of subversion will be fully legal. For example, two wrestlers who fight to a double count-out will then fight in a Falls Count Anywhere match.
 * Bizarrely played straight in the Triple H/Randy Orton match at Wrestlemania XXV; Orton's a sadistic heel who would seize any advantage; Trips has been known to carry around a sledgehammer. Orton spent several months prior to the match systematically destroying the McMahon family (of which Triple H is a member), and Orton hates his opponent with a passion (and routinely uses cheap shots and outright cheating to gain an edge). Both of them fight more or less fairly.
 * Somewhat subverted in Ring of Honor; when a feud becomes so bitter and hate-filled that traditional matches are out of the question, ROH books the feuding wrestlers in a no-disqualification match they call a "Fight Without Honor", where it's basically "do whatever you want, the ref is only there to count the pin or check for submissions". An example is El Generico vs. Kevin Steen at Final Battle 2010 - both men disrespected each other right off the bat by spitting in each other's faces, and it only went downhill from there.

Video Games
"JC Denton: I know you hate being a tool for a bunch of bureaucrats as much as I did. How 'bout we make a gentlemen's agreement?
 * In LA Noire, gets surrounded by three mobsters. Both he and they carry guns. But then he asks them to settle it using Good Old Fisticuffs, to which they happily oblige. He still loses, however.
 * Dudley (pictured above), from the Street Fighter games, is the Trope Namer. A Scary Black Man at first glance, Dudley is a boxer of average stature, but comes from a very wealthy background and is both a scholar and a gentleman. The classically trained fighter often says to his opponent, "Let's fight like gentlemen!" before the round begins.
 * Rubicante from Final Fantasy IV fits this trope. Edge's parents were turned into monsters and unleashed on him (and the party), which almost causes Edge to Heroic BSOD on everyone. He cuts into a This Is Unforgivable! tirade, which Rubicante wholeheartedly agrees with (he had nothing to do with mutating Edge's parents). He then heals your party back to full HP and MP before engaging them in combat.
 * Not to mention that if you cast Fire on him which he absorbs, he responds by repaying the favor and casting Raise on your party.
 * And he heals your party AGAIN before you
 * In Knights of the Old Republic II, there are at least two situations (the Handmaidens on Telos and the Mandalorian Battle Circle on Dxun) where you have duels against one or more opponents with severe restrictions placed on what you can use.
 * To quote Gilgamesh: "And now, we will fight like men. And ladies. And ladies who dress like men."
 * This happens in Super Mario RPG. Halfway during the boss battle with Jonathan Jones (and after you wiped out the four Pirate Mooks he took into battle with him), you have to fight him one-on-one (as Mario).
 * Unless you kill Jones before his last flunky. The Duel Boss bit only triggers if Jones has no Mooks left.
 * Subverted in Deus Ex, by either you or Gunther Hermann. When you encounter him, provided you performed the right actions earlier, you can kill him instantly by saying his killphrase. If you don't...

Gunther: I am the top agent at UNATCO. It is different now. Mr. Simons said if I defeat you I can have any upgrades I want. THAT is a gentlemen's agreement."

"Spy: "Let's settle this like gentlemen!""
 * Meta Knight of the Kirby franchise fits the mold. In most games in which he appears as a boss, Meta Knight will provide Kirby with a sword and will wait patiently until Kirby picks it up (barring Revenge of the Meta Knight, which took place under time constraint). It is difficult to tell if he is a gentleman antagonist/anti-hero or just a Stealth Mentor in the games, though. His anime incarnation is more openly a mentor.
 * Major Ocelot in Metal Gear Solid 3 Snake Eater insists on fighting honorably. This doesn't stop Snake and the nearby Ocelot soldiers from pulling out a variety of dirty tricks to shift the advantage to either side, much to the Major's annoyance. Ocelot also calls others on their crap if they start bending the rules (like he did to Volgin).
 * The Cyborg Ninja also wants to fight Snake in an honourable fistfight in Metal Gear Solid and Liquid does this at the end of both the first and fourth games. Carrying Snake to the top of a high place for a final fist fight on both occasions
 * Assassin in Fate Stay Night. He politely greets all opponents, and then attempts to butcher them. But he chats the whole time, and all he wants to do is have a good fight without outside interruption. If something happens that is disadvantageous to his opponent like Rider spying on Saber to see her Noble Phantasm he will stop fighting immediately and will not take advantage of outside distractions, such as Saber abandoning the fight temporarily in order to help Shirou. He's like a formal Lancer. He also takes defeat well.
 * Most of the more 'heroic' heroic spirits seem to follow some unspoken code of conduct in battle, fighting straight up, giving forewarning on use of their Noble Phantasms, and not targeting each others' masters. Saber, Lancer, Assassin, and to a lesser degree Rider and Berserker, seem to follow this (although in Berserker's case it's probably because he's too mindless to do it otherwise). Even follows this trope in his own twisted way (though that's mostly due to his ego). Archer and Caster do not abide by it and tend to be distrusted and disliked by their fellow Servants as a result.
 * Pokémon of all things subverts this trope viciously up until the Big Bad (Team Galactic Leader Cyrus) of Pokémon Diamond and Pearl and Platinum, who gives you a Master Ball just because you beat him.
 * He's actually giving the Master Ball to you because he thinks it's useless, as it would act as a Restraining Bolt/Power Limiter on the Olympus Mons whose power he wants (he decides to use the Red Chain instead), and this isn't even his final confrontation with you.
 * Team Rocket cheats like no other, and they still usually lose. You'll get ambushed in the games by several Mooks in a row. Heck, the entire Elite Four is basically an endurance contest of five consecutive battles. You can heal in between battles - however, you have to use your own limited items to heal outside of (and during) battles, and you can't buy any PP-restoring items (although you can grow Leppa Berries before taking the challenge).
 * Played straight with . Normally, it's a third party who heals you for plot events.
 * Battalion Wars 2 justifies the inaccuracy of Anglo Anti-Air vet missiles against ground troops with this explanation; aware of the tremendous power of their weapons, they deliberately disable auto-lock when up against ground troops so the enemy will at least have a sporting chance.
 * In the city of Denerim in Dragon Age: Origins, you run into a knight who demands a duel with you out of revenge and honor. He's heard that the Grey Wardens (whose order you are one of the last of) betrayed the king and led to his brother getting killed in battle (this is, of course, untrue). If you meet up with him at the dueling site, he will have three companions with him (as do you, but you are much more powerful than them). Surprisingly, he actually stays true to his word and fights your main character one-on-one unless you refuse to. In that case they will all fight and most likely lose miserably. When you kill the knight in a proper duel, his comrades will just walk quietly away and mourn his passing.
 * In the final boss fight in Assassin's Creed II, Ezio lays down his weapons and proposes a fight without weapons or tricks, to which the final boss agrees. Worth mentioning that the final boss fight is with
 * Who is horrible at hand to hand combat.
 * At one point in AC2 Ezio participates in a brawling tournament during Carnevale, Venice, only for one of the later assassination targets to bribe the host into allowing multiple guards into the pit together and with weapons. Fortunately, the player is not penalized for drawing and wielding his own weapons.
 * It's possible to disarm each guard and beat them to a pulp with your fists (but not kill them). Bad. Ass.
 * Averted in Brotherhood's final boss fight, as for all of 's boasting, he's periodically reinforced by guards who he never bothers to order away.
 * Before the fight with Robert de Sable, Richard the Lionheart makes it seem as if it will be a duel between Altaïr and de Sable. Then the fight starts, and you are facing de Sable with about a dozen other Templars. Luckily, Mook Chivalry is in full effect here.
 * The player can be this in Karateka if he remembers not to approach every opponent in his fighting stance. You can even have the player character and his opponents bow to each other before fighting.
 * Also true in the ending.
 * Team Fortress 2 had unused sounds finally added in the Engineer Update. These include melee dares.

"Gray Fox: Hand-to-hand is the basis of all combat. Only a fool would trust his life to a weapon!"
 * Ironically, The Spy is the least likely to fight like a gentleman. Back Stabs and disguise kits and cloak watches and fake deaths and whatnot.
 * These sounds finally found a use with the dueling 'minigame', which is anything but honourable.
 * Gray Fox tries this in Metal Gear Solid. If Snake puts his guns away, the Ninja will throw his Katana away.


 * Cho'Gath's legendary Gentleman Cho skin from League of Legends quotes the trope name word-for-word.
 * He subverts this however since he is a tank and his whole role is to look like a juicy target for a stupid enemy to try to pick off and get curb stomped by his team in hiding. You also have to keep in mind that Cho is an Eldritch Abomination who can easily stun lock you while he chomps on you, literally. Needless to say, trying to invoke this trope on Cho is a terrible idea.
 * Many players dislike ganks, saying that "You won't fight me 1v1" or something similar. However, these players tend to be using champions who excel at 1v1 combat, so only the Too Dumb to Live players take up their offer.
 * This is the reason everyone fights with danmaku in Touhou, even those characters who supposedly have abilities that would be able to end the fight in an instant.

Web Comics

 * Dominic Deegan has a swordsman named Arcangelo Scarlatti. He is employed as a proxy (substitute) to fight Szark Sturtz, who steps in for master swordsman Donovan Deegan. During the battle, a corrupt knight strikes Sturtz in an old and perpetually open wound, crippling him for a minute or two. Scarlatti can only look on disgust and anger at the knight's actions.
 * It goes beyond that; Scarlatti is outright offended that they thought interfering would be necessary.
 * It's worse than that, it was a duel to first blood. Stark's wound is infernal and the ONLY way to stop the pain is for him to kill somebody. If Scarlatti lost in skill, his employer expected him to die, thus 'winning' the duel by default. After he lost the duel, Stark having been able to control his bloodlust, Scarlatti turned in evidence of his employer having plotted an assassination attempt.
 * It was also revealed that Scarlatti often challenges brash swordsmen who use their skills to bully others.
 * Scarlatti was introduced as a subversion, though. He's famous for the "Scarlatti Disarm," a technique which disarms the opponent and permanently cripples their sword hand. Not very gentlemanly at all.

Western Animation
"Dinobot: "I prefer to beat my opponents the old-fashioned way... Brutally!""
 * Dinobot from Beast Wars prefers to fight like this, even going so far as to rescue the Maximal leader he was fighting for command of the faction with after he slipped off the rock bridge they were fighting on, because he felt he wouldn't have "truly" won the duel if he didn't.

"Rex Guardian: He gave his word! He is honor bound!
 * Subverted in Re Boot. Megabyte convinces Matrix to throw his gun away and "fight like a real sprite." This gets Megabyte punched across the room-- which leaves a dent in Megabyte's armored chest (cue Oh Crap expression from Megabyte)-- and then tackled through a wall, at which point Megabyte pulls out his Wolverine Claws. Then Andraia throws her trident at the two of them for Matrix to use.
 * Played with in Storm Hawks, where the Guardians of Terra Rex live by a strict code of honor, and disparage the titular team for their rougher ways. Of course, this idea then gets the Red Guardians in trouble when they expect the bad guys to live up to this code, and hand over a powerful crystal to them...

The Dark Ace: Honor is overrated. The Cyclonian invasion force is preparing as we speak."

Real Life

 * The rules of martial arts, of course. Although even in martial arts where there are strict rules for sparring, students are often taught to use pragmatic and brutal techniques in a real fight. The rules are there to reduce injuries during sparring practice, and nothing else.
 * Boxing is actually a rare case of this trope being played straight. This helps both entertain the crowd and limit the damage done to the boxers (though many do suffer long-term injury, particularly to the brain). However, if a boxer is actually fighting and not engaging in sport, his opponent is in for a world of pain and will be lucky to have intact kidneys afterward.
 * Most combat sports today have this trope in full effect for the same reasons boxing does. Even the damage of a rough Muay Thai bout, eskrima match, or MMA fight is nothing compared to what those guys could do to each other without rules.
 * Fencing as a sport has rules where just being rude can result in severe penalties up to dismissal from the competition with forfeiture of all fees paid and being barred from future competitions until the governing body decides to let you back in. Its origin is learning how to murder people in the street with a rapier.
 * In societies where duels were allowed, there were rules governing conduct.
 * Massively averted in many cases. In the Renaissance-Early Industrial West, combat with rapiers and its descendents was an inelegant, brutal affair where grapples, chokes, hidden pistols, trips, gouges, and so on were all fair. For a long time, calling someone a "good fencer" was basically calling him a ruffian and murderer. In the East, the flowery, classy duels of cinema were no more real. And those gun-fighting duels of the American West were pure Hollywood as well. Duels with dueling pistols were often gamed heavily as well. What we today would consider an "honorable duel" was actually fairly rare.
 * The various Laws of war, governing the conduct of belligerent nations. The big ones are against perfidy: While Dressing As the Enemy is allowed, fighting while dressed so is not allowed. Attacking a vehicle or building bearing the Red Cross or a related symbol is not allowed, as is using such for combat purposes (storing ammo, or the like). Attacking someone bearing a white flag is disallowed, as is using it falsely. This can be problematic when fighting those who are the worst kind of combat pragmatists.
 * Or, of course, against those who simply haven't heard of those conventions, either through isolation or willful ignorance of the world at large. Or, similarly, when the world at large is ignorant of the isolated culture's norms; history is utterly rife with instances of an "exploration" or "peace keeping" or whatever force ending up engaging in a full blown war of attrition because they didn't realize that, say, the native culture believed that drawing your weapon (not putting it away) was a sign of respect, or that insults and threats were considered "polite banter", etc.
 * North Africa in World War II has a reputation for this partly because Rommel was a Worthy Opponent and partly because the only civilians were Bedouin who knew how to get out of the way and who would be very unlucky if a stray shell landed on them.