Aang: When Zhao had me chained up, it was Zuko who came and got me out. He risked his life to save me. Katara: No way! I'm sure he only did it so he could capture you himself! Sokka: Yeah, face it, Aang — You're nothing but a big prize to him.
Has good, if somewhat extreme intentions but otherwise protects those that cannot protect themselves. Luckily, they respect the hero enough to include him or her under that category.
Was done a good turn by the hero at one point such as the hero saving them certain from death, and the villain feels he owes them a favor. The rescue will probably end with the statement from the villain, "Now, we're even," and the usual antagonism resumes as before. And finally...
Maybe it's genuinely a coincidence, an unintended consequence of an attack on a rival. In this case, the villain is probably not all that happy that he just saved the hero's hide.
And of course it's always possible that it isn't a rescue at all. The villain gave the hero a Hope Spot, the relief of escaping from his enemies, only to destroy that hope himself.
Not to be confused with Save the Villain or Bad Guys Do the Dirty Work. Overlaps with Enemy Mine, as it can be how such a situation begins, but not all instances of bad guys helping good guys falls into this category. May also be a case of Terrifying Rescuer until the heroes figure out what's really going on. Can result in Out of the Frying Pan, if the rescuer proves to be a worse threat than whatever they rescued the heroes from.
Early in the second season, Suo has a series of Contractors trying to capture her, who "save" her from each other. In this case, Hei starts out hunting her as well (like the others, he thinks she is her half identical twin Contractor brother), and the entry of a rival Contractor prevents him from harming her.
Of all people, Sir Crocodile in One Piece. By all appearances, he loves wanton cruelty. However, he pulls an epic move to save Luffy from an Admiral, with no reasoning given other than "If you're going to rescue someone, you should do it right, dammit!"
In Fullmetal Alchemist, Kimblee of all people saves Ed from Pride by weakening him at a critical moment. He did so because Pride had violated his own belief system in order to win, which Kimblee viewed as disgraceful, and proof the Homunculi deserve to lose the war. Keep in mind that Kimblee was already dead at this point with no hope of revival.
Even Envy helped Ed out at one point. This is subverted when he states that the reason behind this was for Envy's own good, not Ed's.
Grimmjow saving Ichigo from death in Bleach by healing him through Orihime, and fending off Ulquiorra from trying to kill Ichigo again, in order to get the pleasure of killing Ichigo himself.
Kurotsuchi saving Ishida and Renji from Szayel is a version of this, since while they are all technically on the same side, Ishida considers Kurotsuchi his mortal enemy since he tortured his grandfather to death.
In Suzumiya Haruhi, Ryoko attempts to kill Kyon twice; the first time it's her normally and the second time it's her in an alternate reality. And Kyon nearly bleeds to death the second time. In the 10th novel, Ryoko comes up and saves Kyon from Suyoh, claiming that he's her prey. Not very calming, but eh. Kyon isn't dead yet, and Ryoko does put a lot of effort, like by throwing a knife at near-light speed and even after it's caught by Suyoh, it still vibrates rapidly, trying to move. That's a lot of kinetic energy.
Bando in Elfen Lied is an Axe Crazy psychopath whose only goal in life is to find and kill Lucy/Nyu. But when the Hunter assaults Mayu, Bando comes to the rescue.
Happens in Dragon Ball Z When Vegeta saves Gohan and Krillin from Guldo before he could skewer them. Of course it was all in an effort to save his own hide. Possibly played straight later, when he saved Gohan from Frieza's latest attack. Note that he didn't think he needed Gohan anymore at that point but saved him anyway.
Happens again when he saves Goku from Android 19, kinda, sorta.
Giovanni saves Yellow from Lance during her arc of Pokémon Special. He leaves her to deal with everything that results from him appearing on the island (or, that is, his Gym Badge appearing), but he does save her from getting herself killed.
In the HGSS chapter, the first three Big Bads, Giovanni, Lance, and Pryce arrive at the Sinjoh Ruins to stop Team Rocket from taking control of Arceus and the Creation Trio.
In Digimon Tamers, Makuramon essentially saves WarGrowlmon, Rapidmon, and Taomon from being destroyed by Juggernaut when he destroys Hypnos. Although to be fair Vikaralamon was also about to be destroyed.
On a similar note, Beelzemon, despite being even more evil than the Devas at the point after he kills Leomon, destroys Makuramon (one of the most evil Devas) and defeats Megidramon, who would have destroyed the world.
In Tiger & Bunny an Unpersoned Kotetsu, accused of murder, is saved from being arrested by the heroes by resident Vigilante Man Lunatic. The reason being that Lunatic does his homework into his potential victims, had previously researched Kotetsu, and knew he wasn't (or at least doubted he was) a murderer.
In D.Gray-Man, Tyki and Road save Allen from being absorbed by the Cardinal after he is imprisoned.
In Mai-HiME, when Nao abducts a powerless Natsuki on two occasions, Shizuru comes to the rescue, once before and once after descending into insanity over her feelings for Natsuki. In Mai's fight with Shiho, a Brainwashed and Face Heel TurnedMikoto intervenes by destroying Shiho's child, which unfortunately also kills Yuuichi
In Naruto, Orochimaru shows up out of the blue and stops Sasuke from killing Team Kakashi. Kabuto explains that Akatsuki is a more serious threat than Konoha, and if they let Team Kakashi live, said team will probably take out an Akatsuki member or two. Sasuke thinks that this is a pathetic reason for not killing them.
Despite being villainous, Zodon and Victor VonFogg are still PS238 students and end up saving the world from an Alien Invasion (with Zodon using a moon-based superlaser to deal the finishing blow when everything else has failed). Victor ends up saving the world a second time when he manages to create a clone of Tyler to convince Prospero to not destroy the world in order to ensure no traces are left of the aforementioned invaders.
In a 1970s issue of Fantastic Four, a villain known as the Over-Mind telepathically took control of Mister Fantastic. This caused Doctor Doom to team up with the FF to try to defeat the Over-Mind.
During the "Heart of the Monster" arc in The Incredible Hulks, Umar the Unrelenting stops yet another Hulk rampage by hauling him off to the Dark Dimension to ... calm him down.
In the X-Men graphic novel God Loves Man Kills, the X-Men are in the process of losing their first fight against the Purifiers, when all of a sudden the Purifiers' high-tech metal suits are shredded and turned into mummifying bonds. Enter the X-Men's then-foe, Magneto.
Magneto: Sheath your claws, Wolverine. Magneto is here as a friend...and, if you'll have me, an ally.
This is basically the plot of Forever Evil. The Crime Syndicate has captured the Justice League and taken over the world with an army of supervillains, and it's up to Lex Luthor and a handful of bad guys who aren't drinking the Kool-Aid to take them down, saving the Justice League in the process. This actually leads to Lex Luthor doing a Face-Heel Turn by the end, actually saving Superman's life on an operating table when he was under no obligation to otherwise.
Queen Of All Oni: Despite knowing that doing so will drain his own power, delaying his escape from his prison, and also that she wants to usurp him, Tarakudo still helps save Jade from Lung (by transporting Left and Right to her location), because he simply can't allow one of his own kind to be tortured and killed by a mere human.
Mario and Sonic: Heroes Unite!: Metal Sonic saves Mario and Sonic from the Giant Bowser Mecha's missile attack in chapter 43—simply because Mario is necessary for his plan, nothing more.
Justice League of Equestria: a variation shows up in Mare of Steel; Luna saving Rainbow Dash/ Supermare looks like a standard Big Damn Heroes moment, when really Brainiac tipped Luna off to Rainbow's whereabouts so she would be back out in the open and susceptible to his Evil Plan.
In Fallen King, Yami Bakura saves the group from Pegasus a few times, but only so he can take the Puzzle.
In Mega Man Recut, Snake Man and Proto Man save Roll in "Robosaur Park."
John Harrison aka Khan from Star Trek Into Darkness saves Kirk, Spock, and Uhura from a group of irate Klingons and then takes the brunt of the ensuing battle for them, since he can kick ten kinds of ass easier than they can and needs them alive because they've got his torpedoes.
He also offers Kirk information about Section 31 that turns out to have been necessary to save the Enterprise from destruction - it eventually becomes an Enemy Mine situation.
District 9. Gang leader pulls variety #3 and saves Wikus from the MNU mercenaries because he wants to eat Wikus' prawn arm.
In Jurassic Park, it's the T. rex that literally appears out of nowhere to save the heroes from the raptors. How it appeared there without anyone noticing, or why the protagonists are now less terrified than they were earlier, remains completely unexplained (there was a barely noticeable hole in the wall it possibly came in through). According to the Word of God, the producers were struggling with the ending when they came to the realization that it was really the hero of the movie, and that was when everything fell into place.
Jason actually pulls this off a few times in the Friday the 13th series. For one, Rennie is being attacked by two gang bangers and Jason kills them (and proceeds to try and kill her afterward) in Jason Takes Manhattan. And who could forget the scene in Freddy vs. Jason when Jason stabs Freddy with his own clawed glove as he is about to kill Lori and Will.
Doesn't go too well in Lottery Ticket. The hero (and lottery winner) Kevin stares down neighborhood bully Lorenzo, who aims to take his money. Sweet Tea, a feared, vicious crime boss who has "invested" (so to speak) in Kevin attacks Lorenzo, slamming him into a table. Lorenzo simply gets up and squeezes Sweet Tea's testicles'till they pop, and beats Kevin ruthlessly. Don't worry though, he's saved by a reclusive ex-boxer he befriended.
In Apocalypto, Jaguar Paw, fleeing from his captors, finds to his horror that the tree he climbed contains a mewing jaguar cub and its ticked off mother. Jaguar Paw jumps out the tree as his hunters find him, but the jaguar intercepts their chase, killing one of the hunters and slowing down the others.
A bigger example occurs near the end of the film, as the brutal yet decaying Mayan Empire is about to meet some Scary Dogmatic Spaniards. Jaguar Paw and his family, however, escape for a new beginning.
Near the end of A Bronx Tale, as Calogero is riding with his violent, dimwitted, racist gangster friends on their way to commit arson, the mafia boss Sonny (who is something of an Evil Mentor to Calogero) accosts them and forces Calogero to get out of the car. Everyone else in the car that night died when a victim of theirs essentially did a Catch and Return of one of the Molotov Cocktails they were using for the arson.
In Louis Sachar's Holes, Stanley spends a few minutes here and there fantasizing about going back to his old school, with his newly acquired hole-digging muscles and possibly some of his newly acquired friends, and getting revenge on Derrick Dunne. In the end, Derrick provides Stanley with the alibi that gets him out of Camp Green Lake.
To sum up what Ryoko does in Suzumiya Haruhi, the tenth novel, she basically says to Suyoh, "Don't you fucking dare kill him! He's mine, bitch!" This is followed by Ryoko starting the fight with a knife flying at near-light speed to Suyoh. Things get epic, really fast. And no, Ryoko doesn't put her body on the line to protect Kyon.
In the first book, at the battle at the climax, the Alerans are saved from one horde of Marat barbarians by another horde of Marat barbarians, because Doroga hates Atsurak much more than he disdains the Alerans and Tavi won the challenge against Atsurak, so he had an excuse. They don't stay villains for long, though.
In both the second and third books, High Lady Aquitaine, who wants to take over Alera, helps the current lord resist another would-be ruler, because she can't conquer the country if someone else already has.
From the fourth book on, the Canim, who have been enemies of Alerans forever, work together with them against the Vord, a much more powerful and monstrous enemy. In Canim culture a respected enemy is considered even more valuable and reliable than a friend, so to humans, successful diplomacy between or within Canim basically looks like one Villainous Rescue after another all the time.
In Titans of Chaos by John C. Wright, this is used twice in the same battle: when Hermes has cornered and badly wounded all the Children, Ares and Mulciber show up to stop him. Then, as they are about to arrest the Children, Echidna arrives to avenge her son's death, distracting Ares long enough for them to escape.
In Shadows of the Empire it looks like curtains for the heroes, Xizor has them surrounded and massively outgunned. Cue the arrival of the Imperials, who not only reduce Xizor's force to a smouldering heap (and kill Xizor himself), they actually let the Rebels go - they'd fire on Rebel ships that crossed into their sights, and if the Rebels hadn't fled before Xizor's forces were mopped up they'd probably have been next, but the Millennium Falcon and a dozen X-Wings were not high priority.
Galaxy of Fear: City of the Dead has Boba Fett saving Zak's life twice - once by shooting Doctor Evazam, once by digging him up after he was Buried Alive - but it's because he wanted the bounty on Evazam in the first instance, and in the second he needed some information Zak had. Later in the series he has no qualms about hunting Zak on Vader's orders.
At the end of A Crown of Swords, Rand chases his current Forsaken target, Sammael, to the deadly abandoned city of Shadar Logoth. He almost plummets to his death inside a building there, but is saved by Moridin, who's the series Big Bad.
At the end of Barb Hendee's Memories of Envy, Eleisha is about to be killed by Simone when who should kick in the door and charge to the rescue? Philip? Wade? Some other member of Eleisha's Nakama? Nope. Juliansaves her.
In A Song of Ice and Fire, the resident Magnificent Bastard and, potentially, Big Bad, Petyr "Littlefinger" Baelish, rescues Sansa Stark from imprisonment in King's Landing by the Lannisters, spirits her away to his newly aquired lands, and disguises her as his bastard daughter, keeping her safe from arrest and potential execution for a crime which, as it turns out, he commited and intentionally implicated her in. This appears to be for three reasons—to use her political claims, to train her as his successor in Magnificent Bastardry, and because he's into her.
The Agent Pendergast novels has Pendergast being saved by his brother Diogenes at the end of the novel Brimstone. Pendergast is sealed inside a wall to die by that novel's antagonist, and Diogenes manages to successfully break him out of his tomb at the very end and nurse him back to health by the time of the next book. Though it is because Diogenes needs his brother alive since part of the big crime he's planning includes murdering people close to him and then setting him up as the killer.
In Animorphs, Visser Three assists the heroes twice due to a common enemy. In #36 The Mutation, he activates the Sea Blade and lets the Animorphs pilot it out of the Nartec city. In #37 The Weakness, he gets so fed up with the Inspector, an arrogant and untouchable supervisor who has been giving a very bad report about Visser Three to his superiors, that he distracts him by groveling so the Animorphs can sneak up and defeat him.
Visser Three's rival, Visser One, pulls this earlier in #5 The Predator when her troops secretly set the Animorphs free, so that their escape will be blamed on Visser Three.
An interesting inversion in Les Misérables: The cop infiltrates the rebels, where he is subsequently discovered and captured. Out of nowhere, the escaped convict who had eluded him for years shows up, is given the opportunity to execute him, and releases him instead. But Wait... in this story, the cop is the villain and the convict is the hero, making it a case of Save the Villain instead.
Angel: Mesektet's last act was saving Angel and Co. from The Beast during its attack on Wolfram and Hart.
Deadly Games. In which villains from the hero's video game appeared in the real world Monster of the Week style. Brent Spiner's villainous prankster character had been snuck into the game by an associate of the hero, so just as the booby-trapped VCR is seconds away from going kaboom, the Jackal, aka Christopher Lloyd, calmly ejects the tape. Turns out he didn't see the Easter Egg character as being one of his, and as he put it, "I couldn't let an outsider to do the honors."
In Power Rangers Zeo, Rita and Zedd interrupt the Machines' impending capture of Jason. The Machines want Jason's Gold Ranger powers, which are becoming unstable. Rita and Zedd just want to stick it to the Machines. Jason sneaks away from both sets of baddies while they're busy fighting each other.
This also happens when Tommy gets kidnapped and brainwashed by King Mondo. Rita and Zedd come to the rescue here too by teleporting the rest of the Rangers to where Tommy is being held. It's pretty apparent that Rita and Zedd hate the Machine Empire even more so than the Rangers themselves.
Also, Power Rangers in Space has Ecliptor save Andros from Darkonda's booby trap (not for his sake, but because Astronema was starting to remember Andros, and he felt it wouldn't be good for her for him to be vaporized just now.)
Another instance in Power Rangers Time Force where a particularly strong mutant named Venomark is turned lose by Frax and bites four of the Rangers, poisoning them with his deadly venom. Wes was saved by Ransik, who has a grudge against Venomark for poisoning him prior to the series and forcing him to constantly drink a serum to stay alive (not that the effects of being poisoned frequently saved the Power Rangers in earlier episodes when he was about to kill them).
In Doctor Who's "The End of Time", the Master saves the Doctor from death by what is almost definitely called the Glove of Rassilon by shooting Rassilon with his life-energy fueledlightning bolts. He's repaying the Doctor for not killing him earlier, and getting revenge on Rassilon for driving him crazy.
In the season 2 finale of The Mentalist, some Mad Artists are about to kill Patrick for their Red-John-inspired film when the real Red John shows up and takes them out.
After the entire Justice League gets captured by the VRA goons in Smallville all hope seems lost...until the Suicide Squad pops up to save their asses.
In Primeval episode 1x05, Claudia is trapped in a house, partially blind, while a swarm of violent carnivorous pterosaurs are flying around and hunting her down by following the scent of the blood she's covered in. She's saved by Helen Cutter.
It should be noted that Helen had not yet had her Start of Darkness and was in fact more of an anti-hero than anything.
666 Park Avenue: Jane is saved from Peter Kramer's ghost when the birds in the walls of the Drake attack and rekill him.
The Vampire Diaries: Damon saving Stefan because if anyone's gonna kill his little brother, it's gonna be him.
This is pretty much the premise of the Necessary Evil RPG. A supers game set in an Expy of the Marvel Universe, the campaign begins after alien invaders kill pretty much every superhero on the planet. Who's left to fight them? The supervillains, of course, led by Doctor Destruction. Although it turns out that it's actually a superhero called the Aquarian in Destruction's Power Armour.
Happens a lot more frequently than you'd expect in Warhammer 40,000, considering the universe is populated almost entirely with xenocidal Knights Templar. The Eldar practically have saving the imperials as their hat, if only to use them as cannon fodder in some later scheme.
In once case Craftworld Iyanden was getting swamped by Orks, so they call even more Wraithguards/Wraithlords in desperation. Then two Kabals of Dark Eldar came in and aided the Eldar fight off the Orks, their reason they were amused enough of Iyandens angst ridden desperation in calling the dead to fight.
Sometimes, Tyranids will avoid eating worlds they come across, and the people below celebrate... unaware that their planet is really a Necron Tomb World just waiting to be activated.
In one particularly hilarious subversion, a Tau world was under attack from a Tyranid splinter fleet. A Necron fleet appeared in orbit and proceeded to slaughter everything alive. The Tau celebrated, and as the Necrons landed, sent a welcoming party with their highest Ethereals. The Necrons proveeded to slaughter everything alive.
This also comes up in Warhammer Fantasy. The Vampire Counts have been known to jump in and help the Empire if the forces of Chaos and the Skaven threaten them sufficiently. After all, they're vampires, and vampires need living mortal prey to snack on... What ever will they do if all the warm walking blood-bags are killed off?
While that applies for most vampires, some such as Vlad von Carstein are Wll Intention Extremeist who want to convert everyone to vampires so as to starve Chaos (they can't feed off the emotions of the undead.)
In Super Robot Wars 3, Anavel Gato's claim to fame in his show of origin is launching a stolen nuke at a peace conference. He reenacts this scene in the game, but this time the "peace conference" is between two villainous factions, meaning that his actions have prevented a very dangerous Villain Team-Up.
As a subversion of being the Fake Defector, Archer from Fate/stay night pulls off one of these, effortlessly killing Caster and Kuzuki Souichirou before trapping a powerless Saber and trying to kill Shirou.
More straight example would be the first appearance of Gilgamesh in the Fate arc of the game - when Caster had Shirou and Saber in the palm of her hand the enigmatic Golden Servant appeared and sadisticaly executed her because he already decided that King of Knights is his prize and was enraged by the fact that Caster dared to assume she can make Saber hers.
The SA-X at the end of Metroid Fusion stepped in and attacked the Omega Metroid just before it destroyed Samus, although in this case the rescue was because the X parasites were the natural enemy of the Metroids, and it failed to destroy the Omega anyway, but when the X was destroyed instead it gave Samus back her Ice beam which allowed her to defeat the Omega.
in AdventureQuest WorldsDrakath pulls this when Nessie is trying to attack The Hero unnoticed Drakath stops Nessie from killing The Hero
Etna pulls one off in Disgaea 2 to save the party from fake Zenon. She is not happy about it. It borders on Big Damn Heroes as well, due to being a playable character later and a protagonist of the first game, but she's treated as a secondary villain and serious threat to the protagonists' plans at this point in the story, and rightfully so as she manages to kill, or nearly kill, the fake Zenon in this encounter and she is the highest level opponent, at level 1000, the party will face (that isn't a bonus boss) aside from Laharl.
The Elder Scrolls V: Skyrim features an accidentalVillainous Rescue instance at the beginning of the game. The Big Bad Alduin swoops in to kill the player at the beginning of the game, but not only does he fail to hit the player, he also throws off the balance of an executioner who is also about to kill the player. Alduin didn't intend for the player to survive, but through his own actions caused the player to escape.
In the True Ending of Asura's Wrath, the Golden Spider rescues Mithra from Olga. It's a villainous rescue because the Spider only did it to because he wants to possess Mithra. At the same time he also reveals that he is responsible for the appearance of the Gohma.
Sonic the Hedgehog 2 has this in the 8 bit versions. The platform is too far away, and Sonic falls to his doom. At the last second, he is saved by Robotnik, who would rather have his robot defeat him than letting Sonic burn into a crisp.
Kingdom Hearts II has a point where Organization XIII reveals the Sadistic Choice Sora has to make (this being that if he defeats the heartless, thus saving the innocents in the worlds, the Organization collects the hearts to grow closer to their final goal), and he is subsequently reluctant to fight anymore. This almost results in him, Donald, and Goofy being overwhelmed by the Heartless until Maleficent helps them escape. Her given reason is along the lines that the Nobodies and the Organization were a bigger pain than Sora, and that she wanted them gone before she bothered with revenge.
It happens again during the game's final level. Same villain, even.
In the Corneria level of Star Fox Assault, Fox is about to get into his Arwing and rejoin his teammates in the skies above after destroying several radar jammers. Suddenly, the ship is destroyed and he's surrounded by aparoids, only to be saved by none other than Wolf O'Donnell and the rest of Team Star Wolf. Wolf says that he's only helping Fox because he plans to kill him later.
In Star Wars: The Old Republic, there are several occasions where Light Sided Imperial characters can choose to intervene to rescue Jedi or Republic troops from danger. Naturally, these often lead to a lot of confusion from the people rescued, especially if the player happens to be Sith.
In the last Episode of Umineko no Naku Koro ni, Erika of all people swoops in to save Ange from the Goats. Lambdadelta also risks herself to save Battler and Ange from Bernkastel and Featherine.
An odd example occurs in Pokémon Platinum. Big BadCyrus is about to destroy the universe to create one "without spirit", when a portal opens and Giratina pops out to stop him. While Giratina is not villainous per se, it is the Pokémon world's resident Satan analogue, yet it effectively does this for all of existence. Sort of. It does start ripping reality to shreds by accident.
Monkey Master leads the Aliens in combat against the Martians in It's Walky!'s Final Battle, having decided that their chances of returning home (or at least surviving the Martian invasion) in Head Alien's absence higher if they worked with SEMME.
In Emergency Exit, Lord Kyran and crew lead an effort to rescue Eddie from being sacrificed, mostly because they figure he's about to find an artifact.
Beyond the Canopy. Glenn and Glade are about to be crushed by a giant robot, then someone offscreen blasts a hole in the robot's chest. Said someone turns out to be a lackey of the Baron, come to take an artifact from Glenn, and to enslave Glenn and everyone else in the vicinity.
In Worm, this occurs when the Wards and Protectorate are fighting the Slaughterhouse 9 and doing poorly-Skitter shows up on a giant flying beetle with a bandoleer of grenades.
And at the climax of the story, Taylor herself is saved from Scion by the Endbringers.
Rocket Power: During a sand castle contest, the heroes' submission, a model amusement park, which they had spent the whole episode on, is threatened by the rising tide. They're powerless to stop the water from destroying it before it gets judged, when suddenly, one of the characters' older brother shows up with his cronies, and they protect the model with their surfboards.
Later on, Mai, one-third of Azula's Quirky Miniboss Squad, turns against Azula, her own uncle, and pretty much every guard in the prison in order to save the Gaang, though specifically her ex-boyfriend. For added awesome, it doubles as a Heel-Face Turn.
Also shows up (somewhat) in the Sequel SeriesThe Legend of Korra; Tarrlok captures Korra and plans to leave the city with her as a hostage, but then Amon and his Equalists arrive at Tarrlok's hideout, and the ensuing confrontation allows Korra a chance to escape.
In Reboot, Megabyte teams up with Bob and co against The Web because the web creatures are dangerous for everyone. He backstabs Bob later, though.
The residents of South Park are saved from the Jersey invasion by Al-Qaeda.
Cartman rescues Kyle's family from the about-to-be-destroyed San-Francisco, because he misses picking on Kyle.
In The Transformers, Starscream saved the day in the episode "Enter the Nightbird", when he used his null-ray to deactivate a female-ninja-robot (the Nightbird from the title) who was successfully attacking the autobots. His motivation: Megatron demoted him and placed her in his place. He was obviously jealous.
Megatron of Transformers Prime prevented his version of Starscream from landing a potentially lethal blow to Optimus both because he intends to defeat Prime himself and because he intends to pay his treacherous underling back for an attempt on his life.
He does it again in the Season One finale. This time by taking out the Unicron-Colossus that was giving the Autobots trouble.
Starscream even gets one in, himself. He saves Arcee from being killed by Airachnid and even decides to not kill her himself, presumably because he was in a good mood after hitting Airachnid with one of his shots.
One Powerpuff Girls episode sees the villains of the week (the Gangreen Gang) defeated by Mojo Jojo, Fuzzy Lumpkins and Him, since the Powerpuff Girls themselves never realize what's actually going on (namely that said Gang used the Mayor's emergency phone to prank call the Powerpuff Girls into beating up villains who weren't doing anything). The narrator seems uncomfortable with making his usual Once an Episode declaration, given who saved that particular day.
Sorta example in the The Spectacular Spider-Man episode ''Gang Land", where the current Big Bad Tombstone is in a three way fight with Doctor Octopus and Silverman. When Spider-Man decides to get involved to stop collateral damage from the fight, Dr. Octopus suggests a temporary truce between the three villains so they can kill Spider-Man, since he's the cause of most of their problems. Tombstone rejects, wanting to stay a Villain with Good Publicity and can't do that if he fights Spider-Man in public, and actually saves Spider-Man from Dr. Octopus. It's only a partial case since when both Spider-Man and Tombstone fall into a sewer and out of view everyone, he Spider-Man start fighting.
Played straight when Spider-man and the Rhino team up to destroy the specs for the Rhino suit. Spider-man doesn't want to have to fight an army of Rhinos, and Rhino doesn't want to have to compete with them.
In the Teen Titans episode "Masks", Robin nearly falls off a building during a fight with Slade, only for Slade to prevent it. Slade's then-excuse is that he's "not done with (him)" and continues the fight. In a later episode, Slade reveals that the real reason he doesn't want Robin dead is because he wants him as his apprentice.
In the Dungeons & Dragons cartoon, Tiamat's main purpose seemed to be to save the kids from Venger. This wasn't intentional. Most of the time she probably didn't even notice they were there. She just had a tendency to show up and try to kill Venger right when he had the heroes cornered.
Played for laughs: In the Daffy Duck cartoon "Daffy Doodles," Daffy (as the cartoon's antagonist) pulls officer Porky Pig back from falling over the side of a building during a chase. "Awfully sporting of the little black duck!"
In The Venture Bros., the Monarch and Dr. Mrs. The Monarch step in to claim Doctor Venture for himself right before dozens of members of the Guild Of Calamitous Intent and its leading councilmen lowered him into a vat of acid. They succeed thanks Dr. Mrs.' rules lawyering against the leaders of the guild themselves, and further wind up accidentally saving Brock and Shore Leave, who were simultaneously attempting a much riskier, separate rescue.