I Let You Win

The player has just defeated The Dragon, or perhaps another servant of the Big Bad. While The Hero is quick to spare his enemy's life, he can take some satisfaction in knowing that he is, in fact, strong enough to take on the villainous forces that plague his world.

...at least until he finds out the truth.

You see, there was a reason why he won. This character was involved in some kind of Plan, and part of the process required him to lose the battle. That's right! You're not as tough as you looked! Robbing you of the satisfaction of victory makes him just as much of a Magnificent Bastard as the fact that you have been unwittingly aiding his scheme!

...but wait. Something doesn't add up. His attacks were fierce. It took you a few tries to get past him, each time having to witness that dreaded Game Over screen when you failed. You know, if he's so interested in letting you win, maybe he could show enough courtesy to give you a bit more of an advantage in the battle?

True, if you won too easily, you might think that something's up. Or maybe he's so proud that he believes that if you failed to defeat him at merely a portion of his power, you don't deserve to be his unknowing pawn anyway.

Or maybe this is just Gameplay and Story Segregation. After all, there would be a lot of drama lost if you demonstrated that you were truly capable of destroying your enemies so early in the plot. Sure, a Hopeless Boss Fight would make a lot more sense, but where's the fun in that?

Most instances of this trope are also examples of The Battle Didn't Count, although for some villains, Death Is Just The Beginning...

Naturally, even reading the game names here is likely to be a SPOILER.

Anime and Manga

 * Evangeline was the first villain in Mahou Sensei Negima. Nearly three hundred chapters later she's still the most powerful character to appear, who even Jack Rakan could only just barely beat. Some are beginning to suspect that she is in fact more badass than the Thousand Master himself and are starting to look at her defeat and memories with great suspicion. There is strong evidence that she has a crush on the Thousand Master.
 * Strong evidence? The obsessiveness of her crush was the main reason he sealed her away at all: it was the only way to get her to leave him alone.
 * In One Piece, Garp let Luffy win so he could save Ace, since Garp is a marine and Ace a pirate and his grandson. His relation to Luffy was also a factor.
 * Garp's superior, Fleet Admiral Sengoku, isn't fooled for a second. But Garp is the legendary hero of the Marines, so there'd be too much bad PR if he were punished.
 * In Naruto, this is stated to be the real reason why could win against.
 * In Yu Yu Hakusho the Toguro Brothers faked their loss at the end of the "Rescue Yukina" arc for Sakyo and so they can challenge the heroes in a Tournament Arc.
 * In Yaiba, during the Oda Nobunaga Tournament Arc, the Brilliant but Lazy Master Swordsman Soshi Okita manages to best Yaiba, but is so amazed by the latter's spirit and determination that decides to forfeit.

Live Action Television
"Playing Guard: I had this whole setup, could beat him in one move! But did I do it? No, I didn't! Watching Guard: ...Well, you did. Playing Guard: ...Yeh, I did. Beautiful move. Watching Guard: Beat him in his last game'a chess...YouBastard."
 * Television example: In an episode of Farscape, Rygel lets a villain win a chess-like game as part of a con.
 * Skip does this to Angel in season 3. It had something to do with the Jasmine arc in season 4, in which Skip was Jasmine's ally and Nigh Invulnerable, but is never fully explained.
 * Employed in Rutland Weekend Television, in which a prisoner who is going to be hanged tomorrow is playing chess against a guard, while another guard idly watches. The guard eventually says he's letting him win, to the prisoner's disbelief -- both of the guards then reminisce about a time when he didn't let the prisoner win, effectively making him a Jerkass.

Mythology

 * The myth of Hippomenes and Atalanta has this as one of its interpretations, where Atalanta had evidently let Hippomenes beat her (With Aphrodite's help, of course.)

Video Games

 * Pretty much every boss fight in the first 75% of Metal Gear Solid. Some are more obvious about it than others; Vulcan Raven practically tells you that he let you win after you defeat him the first time. This group is incredibly devoted to this trope, as the majority of them die simply to convince you that you're not doing the dirty work for them. And was that Hind really necessary?
 * Other games in the series use this trope almost as much. Metal Gear Solid 3: Snake Eater even applies this trope to the final boss, kind of.
 * Used again in MGS4, when
 * After you defeat Death in Castlevania: Portrait of Ruin, he informs you that he has a reason to hold back. Indeed, he does: he can only bring back Dracula if you kill the guy who's usurping his power. This does not explain why he seizes you with chains and ends your life with one quick Sinister Scythe swipe if you are unable to free yourself first.
 * Near the beginning of the Ninja Gaiden X-Box remake, you fight Ryu's uncle Murai to a standstill. He calls it training, but during the fight never hesitates to kill you if you let him.
 * Devil May Cry 3 has the recurring boss and/or advisor, Jester, who claims he needs Dante alive but doesn't hold back. Given that Jester was only a boss in the "Special Edition", which was somewhat panned for its quality, it is difficult to say if this trope occurs intentionally or out of developer laziness.
 * In Mega Man X 5, the first boss fight is against Sigma in the form of a large floating head. After the player defeats him, a virus breaks through Earth, which was what he wanted. Zero clearly states "he lost to us on purpose!"
 * Tales of Eternia, about halfway through the game, the temporary party member Ras reveals that he's the incredibly powerful knight you've been hearing about, and attacks you to prevent you from escaping to Celestia. After you beat him to a pulp and get to the next town, your party realizes that he couldn't have been fighting you for real - he kept pulling his punches and not taking advantage of openings, leading them to conclude that he let them win.
 * In Tales of Symphonia, this takes place -- provided that you do win, which for a first-time player isn't a given (the story goes the same way regardless). Lloyd is all too aware of this. Amusingly enough, he is far easier the next times you fight him when he isn't holding back -- of course, you've gained quite a lot more power in the meantime.
 * Inverted in Dawn of the New World, where.
 * Used by the Black Knight in Fire Emblem: Radiant Dawn's localized version (replacing a retcon of questionable quality the Japaneses version uses) to explain how he was back after being defeated and Left for Dead by Ike back in Path of Radiance. (Although his return was obvious if only because his identity was never revealed.) For comparison:
 * Translation: During that climactic battle in Path of Radiance, Ike reveals that his father crippled his sword arm, a fact that the Black Knight didn't know. As the Black Knight's true goals was to surpass his teacher, aka Ike's father, this revelation makes the Black Knight realize that his victory over Ike's father was hollow, as he never got to experience Greil's true ability. So he allows Ike to win in the hopes that later Ike would become as powerful and skilled as Greil, in short a substitute for Greil to test his skills against.
 * Original: The Black Knight's warp powder malfunctioned, leaving Ike to fight his spirit, that was not only weaker then his true self, but returned to his body after defeat.
 * The entire campaign of Warhammer 40,000: Dawn of War is one giant I Let You Win by
 * Almost: . After all, Khorne cares not from whom the blood flows, only that it does.
 * The game In Famous has Cole fight Kessler at the end, who constantly taunted him throughout the game and later implies that he hopes Cole kills him.
 * Thunder Force V has you battling the Guardian, an AI infested with alien coding (from the ship of the previous game). Towards the end, however, it's revealed that  Since it couldn't destroy itself, it deliberately paved a path for the pilot.
 * Warcraft III begins with a nice example of this in the Human Campaign with
 * The Lich King, now Arthas himself, continues to do this in World of Warcraft. A good number of times players defeat his lieutenants and wipe out large numbers of his soldiers. In the final battle, Arthas reveals that it was all a plan to get them stronger, to let them become the champions of the world...
 * In Mega Man Zero 4, The Dragon Kraft is apparently going along with the Big Bad's evil schemes because he's descended into a "survival is everything" paradigm and thinks it's the only way to protect his and his ex's skin. After the first battle against Kraft, Zero asks him what's holding him back. Later, Kraft pulls a (sorta) Heel Face Turn into a Knight Templar and threatens to Kill Sat an entire city of civilians to get at the Big Bad, and you have to go stop him. This time, he believes in what he's fighting for, so naturally, he's harder.
 * Subverted in Kingdom Hearts: Chain of Memories; after the first fight with Larxene, she is seen in a later cutscene musing about how it was hard to hold back enough to throw the fight - but then Axel and Vexen both mock her for trying to justify getting her ass kicked, even though what she claimed was true as evidenced by her second fight with the key bearer. Axel's hypocrisy isn't lost in the gamer as he also let Sora win in his first match. Vexen just seems to despise Larx due to her association with "that dog Marluxia", so he probably didn't want to miss the chance of making fun of her.
 * Vexen also holds back against Sora the first time in order to get data on him and create the Twilight Town card.
 * In Reverse/Rebirth, Axel tells Zexion that even in the second fight, he decided to let Sora think that he'd finished him off.
 * In Wild Arms 4, Gawn, the only Brionac villain without a special power, stops fighting you after he runs out of bullets. He obviously let you win, because he could have just reloaded, or better yet, used his bare hands since he can punch missiles with them. Since he shoots you before you can ever do anything offensive against him, this might seem like a Hopeless Boss Fight, but surviving through it actually counts as a win for you.
 * In EverQuest 2 the resident Lord of all Vampires, Mayong Mistmoore, reveals to players at the end of the major Rise of Kunark questline that he's the God of Blood, and he allowed the ancient and powerful sword SoulFire to be taken from him simply because he finished studying it. He then promptly begins studying another ancient artifact, a doomsday calendar called the 'Chelsith Stone'. (One must wonder about the impact of letting an ancient and powerful Vampire/God study equally ancient and powerful artifacts).
 * In Baldur's Gate 2, Kangaxx is a disembodied lich, whose body was torn apart, its bits hidden in tombs. If you reunite his body for him, he rewards you (or attempts to) with death. If he fails, he laughs madly, as he apparently needed to get his body back first, then have it destroyed, to be transformed into a demi-lich, which is much harder to kill and much more likely to ruin your day.
 * The campaign mode for Naruto: Ultimate Ninja 3 makes heavy use of this trope. In order for the story to advance, Naruto has to defeat most of the other Leaf ninja in single combat, including adult chunin and jonin who are canonically stronger and much more skilled than he is. However, since the competition is a friendly one and Naruto has more emotionally invested in it than they do, the battles with stronger ninja such as Shizune, Anko, and Kakashi tend to end with Naruto absolutely exhausted and the stronger ninja saying "Okay, that was pretty good, you obviously care more about this than I do, so here are my Plot Coupons," having not even broken a sweat.
 * At the end of the campaign,.
 * Done without Gameplay and Story Segregation in the original Final Fantasy, when, and is actually not that hard of a boss.
 * And in XIII: Barthandelus!
 * Likewise the Emperor in Final Fantasy II: He sold his soul to the devil (or equivalent) to gain the power to summon The Legions of Hell to aid in Taking Over The World. It logically follows that at his death, he's gonna go to Hell, hence the protagonists are eager to help him get there. The remakes/updated rereleases only make him even more Crazy Awesome.
 * In many of the Pokémon games, certain trainers will claim they let you win. However, it usually seems like they're lying to save face, rather than that their defeat serves some kind of plan.
 * Some of the Pokémon themselves can be caught simply because they allow you so. Especially  in Pokémon Black and White, who  to catch them.
 * Used contstantly in many of the Touhou games, partially because most denizens of Gensokyo view fighting as a game and mostly to justify defeating some of the most absurdly powerful beings imaginable (manipulation of fate, manipulation of boundaries, killing anyone with a thought, control of nuclear fusion etcetera). Explicitly stated in Subterranean Animism, in which the stage 3 boss Yuugi says she was just playing around, her sake NOT EVEN DROP!
 * Surprisingly used after beating the Penultimateboss of Bayonetta.
 * In Suikoden I,
 * And Suikoden II features an inversion in that it
 * Mild example in the form of Slayer in any battle. His story dialogue and battle animations suggest a strength far greater than most of the cast, and his defeat pose has him simply lying down with an "I'm tired of this" look as opposed to being knocked out like everyone else. Especially evident in stories where he fights Sol Badguy, arguably the strongest person in the GG universe next to Slayer.
 * In Super Paper Mario, Mr. L claims that he was scouting the heroes, and he was a ridiculously strong boss (his attacks do more damage than anything else likely to hit you until you reach Count Bleck) for that particular part of the game. Considering Luigi's abilities in other games, he's probably telling the truth.

Western Animation

 * Spoofed in South Park. Satan challenged Jesus to fight for the fate of the world. It was a scam. Satan knew everyone would bet on him, given how strong he was compared to Jesus (this was before he turned Badass in "Red Sleigh Down"), so Satan bet on Jesus and threw the match, returning to hell with all the money.
 * Man! That guy is a jerk!