What's worse than one Big Bad? Two Big Bads, possibly more, working in intentional collusion with each other. Sometimes they will work together just fine; being all respectful and well, but more often than not there will be rivalries between them, and they will tend to break out into a literal example of an Enemy Civil War.
Not to be confused with The Dragon (a main villain clearly subordinate to the Big Bad), though if one of them becomes dominant he may reduce the other(s) to the position of Dragon with an Agenda, Dragon-in-Chief and/or The Starscream. May overlap with Unholy Matrimony. Contrast Big Bad Ensemble, where there are also several Big Bads operating simultaneously, but not necessarily working together or even interacting in any way.
See also Villain Team-Up and Big Bad Ensemble. Contrast Co-Dragons, where one Big Bad is directly served by two or more equally ranked lieutenants.
Yami Bakura and Marik Ishtar in the Battle City arc of Yu-Gi-Oh!, until Yami Marik disposes of them both.
Dark Bakura and Akhenaden are this in the final arc of the manga.
Placido, Jose, and Luciano in 5D's, although technically, they are three embodiments of the same person, Aporia.
Kotomine Kirei and Gilgamesh in Fate/stay night. Kotomine makes the plans, Gilgamesh calls people mongrels and swordspams them to death. Or doesn't. He helps if he feels like it, anyway.
Sailor Moon: Several incarnations of the true Big Bad, Chaos, is the true main villain for the Story Arc, while the person we believe is Big Bad is The Dragon. However, a few have been to equal Big Bad levels, namely Queen Beryl and Queen Metallia of the first story arc.
It's debatable whether Tobi and Pain's relationship from earlier in the story was an example of this with Tobi being dominant or simply a straight-up single Big Bad and his Dragon-in-Chief. Tobi is the master plannerbehind the scenes while Pain is the unquestioned leader of Akatsuki with enough power to flatten most armies. Each has their own diabolical plan that actually conflicts with the other, and it's never revealed if either one knew what the other was planning.
And now, with Kabuto's defeat, it seems that we have a new Duumvirate with (T)obi(to) and the resurrected Madara. They've been working on the same plan since before Madara's death, so you could say it's the longest running Duumvirate in the series.
With the recent revelations turns out the longest running Duumvirate in the series was actually the one between the Black Zetsu and Kaguya Ōotsutsuki. How long? Well, just spanning the entire history of conflict in the Shinobi world!
Bleach: The third Bleach movie, Fade to Black, has this split between Homura and Shizuku, two siblings that Rukia adopted before becoming a Shinigami. This pair actually provides a pretty interesting variation: It's clear that these two are the ones responsible for the conflict within the third film, but Shizuku is much more action-oriented, being the one to wield that memory-erasing Sinister Scythe. His sister, Homura, acts as support with her Mass Teleportation. Furthermore, while Homura is paranoid, obsessive and temperamental, Shizuku is a lot calmer, rational and emotionally stable, but of the two, she's the one calling the shots, while he's loyal and obedient to the letter, even when he disagrees with what she says.
It's a subversion though in that the two were no honest threat to the protagonists apart or together. It's only when things went south in their partnership and Decken went nuts and tried to destroy Fishman Island via a Colony Drop did they become anything remotely resembling a threat.
Eyeshield Twenty One's last arc has a de facto Big Bad Duumvirate on the American Pentagram. Elitist goliath Mr. Don is the team captain and the undisputed leader of the team, yet despite his Genius Bruiser status, he spends most of his time serving as the centre, which leaves his ability to lead the team somewhat handicapped. As such Evil Genius Clifford D. Louis makes and executes most of the plans; he's also the only player who isn't frightened of Mr. Don and whom the latter doesn't try to order around, making them an example of this trope.
In GaoGaiGar FINAL Palparepa is officially considered the leader of Eleven Masters of Sol and Pauls Abel is considered to be his Dragon, but in reality they have divided the Big Bad duties between each other and Abel clearly acts like Palparepa's equal.
The Table of Contents and Noah in Soul Eater because the Index was the true mastermind behind Noah.
The three lords of hell in The Sandman and Hellblazer: Lucifer Morningstar, Azazel and Beelzebub. Somewhat subverted in that Lucifer is by far the most influential to storylines and Azazel is taken care off in The Sandman. Beelzebub has had little to no importance.
The Kindly Ones also swerve back and forth with this, given that they only tenuously qualify as separate beings anyway and they only really qualify as antagonists starting with the second to last book; depending what you think of Morpheus' motives, not even then.
The Sin City story Hell And Back has the corrupt police chief and assassin guild leader working side-by-side along with The Don of the series, Herr Walenquist, who is revealed later.
Mr. Sinister and Apocalypse fill this role for a good portion of the X-Men comics, though Sinister is also clearly identified as The Starscream.
Megatron and Galvatron in the UK The Transformers comic story Time Wars is an example of the big bad teaming up with his past/future self. Predictably a lot of other characters don't survive the story.
In Book 3 and 4, Anti-Villain General Rasga teamed up with Darkhell. Darkhell eventually betrayed him, and Rasga sided with the good guys for the end of the battle.
later, Book 5 and 6 involved Pirate Captain Ceyderom teaming up with Prince Halan. Ceyderom later betrays Halan by siding instead with past Darkhell (or at least trying; it seemed like Darkhell was merely tolerating his presence), and Halan redeemed himself by committing a Heroic Sacrifice;
The Anathos Cycle starts with Hero turned Anti-Villain Elysio being forced to team up with Darkhell under the Guardian's orders. Surprisingly enough, this case was the opposite of the usual schema : not only did Darkhell not betray Elysio, but both eventually redeemed themselves by helping the heroes against Bigger Bad Anathos and committing a Heroic Sacrifice.
Lex Luthor and The Joker have done this several times, though the former seriously despises doing so, while the latter often demands to be let in on the plan.
Original Big Bad Hari Vallalkozo and replacements Big Bad Douglas Zemeckis from Orphanimo briefly form one near the end of the second-last album.
Crismus Bonus and Marcus Ginandtonicus in Astérix the Gaul seem to work this way, even though Crismus Bonus calls them a triumvirate. However, as shown in their thoughts at one point, when they succeed in rising against Ceaser both of them plan to get rid of the other to, as Crismus said, "become a triumvirate all on his own"
Dungeon Keeper Ami has Alphel and Arachne team up while a third keeper, Nero, serves as a distraction to the bulk of Mercury's forces. Mercury still manages to stomp them in one of the most spectacular crowning moments of the series yet!
In Disney fanfic The Hellbound Hearts, it's essentially a team-up of numerous Big Bads from previous Disney films all either teamed up or fighting against one another. Still, because each one has their own agenda, it's hard to figure out which character will end up being the main antagonist. That being said, this trope is played straight with Xanatos and Maleficent, with both under the belief they're in charge of their particular faction.
Ward Abbott and Yuri Gretkov in The Bourne Supremacy. True to form, Gretkov refuses to come to Abbott's assistance near the end of the movie, leading to Abbott's capture by Bourne and suicide by gun.
Miraz, Glozelle, and Sopespian have elements of this in the film of Prince Caspian- Miraz is dominant, but he is forced to (grudgingly) rely on the other two. When they've finally had enough of him, they kill him and become a full Big Bad Duumvirate for the remainder of the film. The three have elements of this dynamic in the book as well, though the movie gives all three more screen time and therefore emphasizes it more.
Cyrus "The Virus" Grissum and Nathan "Diamond Dog" Jones in Con Air. Nathan is technically taking orders from Cyrus, but they both have equal authority and Nathan admits he is only doing so for the time being.
Similarly, in The Dark Knight Rises, Bane and Talia al Ghul are either this or Bane is The Dragon to Talia; the movie allows a multitude of interpretations. Although Catwoman appears, she isn't part of the Big Bad club by any means.
In Total Recall (1990) there's Vilos Cohaagen and Hauser, who formulated the plan to take down the Mars Resistance together.
In "Oz: The Great and Powerful", Evanora, The Wicked Witch of the East, and her Ax-Crazy sister, Theodora, The Wicked Witch of the West join together to try and take over Oz, and kill Glinda the Good. They fail.
In the third Austin Powers movie, Dr. Evil teams up with Goldmember against Austin Powers.
The two MUTO monsters from Godzilla (2014) are more or less this, though the female is arguably the bigger threat (and literally the bigger monster) as she carries with her thousands of baby monsters and is the most protective of them.
Lockout: Alex and Hydell, the pair of prisoners who lead the riot and are brothers. Between the two, Alex takes center stage as the man with the plan much more often, but Hydell is so utterly psychotic that he's a much bigger threat because of his wanton murder and destruction. Hydell eventually murders Alex himself to become the main villain for the final minutes.
Artemis Fowl: The Arctic Incident: Opal Koboi and Briar Cudgeon. It is revealed late in the book that Cudgeon plans to kill Opal once gaining power, a fact which proves critical in his downfall via Engineered Public Confession.
Counselors and Kings: Probably the best way to sum up the...odd relationship main villains Kiva and Akhlaur have in this Forgotten Realms trilogy. They hate each other (or at least, Kiva hates Akhlaur personally - he holds her in contempt, but that's how he treats everyone) but work together to advance their own goals- power (for Akhlaur) and vengeance (for Kiva). As he treats her like a servant, it probably would count more as Dragon with an Agenda except that Kiva herself in no way sees herself as subordinate and has tons of plans apart from Akhlaur, and in fact tries her hardest to manipulate him (though its made clear he knows what she's doing, and is playing along for his own entertainment). They're best summed up as two distinct Big Bads who for the moment happen to be going in the same direction.
For Harry Dresden, it's a good week if he only has two major enemies trying to kill him. Since the Black Council is now confirmed in-universe, technically every single book in the series has at least one obvious villain and the Black Council.
The necromancers Cowl, Grevane and Corpsetaker in Dead Beat. Though while they're all technically working together to find the Word of Kemmler, they all intend to betray the others and take the Word's power for themselves. Of the three, Grevane dies in Dead Beat, Corpsetaker loses her body but survives as a ghost until she's Killed Off for Real in, appropriately enough, Ghost Story, and Cowl is still out there as a recurring villain and possibly the series Big Bad (and almost certainly aligned with that person or group if he's not).
Hand of Thrawn: In this Duology, three people are working to create and maintain the illusion that Thrawn has returned, but of the three, Disra and Tierce are the ones at odds. Flim mostly serves as The Watson, and doesn't seem to have much ambition of his own beyond surviving and being handsomely rewarded.
Flim, being a typical con artist, is interested in a short-term reward, claiming that people of his "profession" don't stick around long enough for the mark to take a closer look at them. As such, he knows that he has no prayer in actually running the Empire, especially since he doesn't have the political or the military skills for the job.
John Carter of Mars: A very tense one shows up in The Warlord of Mars, the third book in this series, consisting of Matai Shang (Priest King of the white Martians, or Therns) and Thurid (a warlord of the black Martians, or First Born). Later in the book it becomes a triumvirate when Salensus Oll (Evil Overlord of the yellow Martians, or Okar) joins up. Since these three have their own goals and ambitions, there's a fair bit of backstabbing all around. In particular, the white Martians and black Martians hate each other, they just hate John Carter more.
Legacy of the Force: While not exactly a Big Bad herself, Admiral Cha Niathal works with Jacen Solo in order to pull a Coup d'Etat on Galactic Alliance Chief of State Cal Omas. This alliance eventually does fall apart with Niathal forming her own faction of the Galactic Alliance opposed to Jacen.
Subverted Trope. Saruman sees himself as Sauron's ally and has full plans of double-crossing him once he gets his hands on the Ring- but Sauron is both far more powerful and more intelligent, knows full well about Saruman's plans, and considers him varyingly a useful tool and a nuisance, but never an equal of any kind, making Saruman a Big Bad Wannabe.
Played more or less straight with Morgoth and Ungoliant in The Silmarillion: they team up to destroy the gold and silver trees, humiliating the Valar and setting off the War of the Silmarils, but it ends poorly when Morgoth tries to double-cross Ungoliant. Weakened by pouring his power into making his army and Ungoliant empowered by the light of the Two Trees, only a posse of Balrogs saves him from being devoured.
However, while Morgoth and Sauron did work together, they do not fit this trope. When Morgoth was still active, Sauron was his subordinate. Sauron became the Big Bad towards the end of The Silmarillion (and throughout The Lord of the Rings) as a result of moving into the power vacuum left when Morgoth was imprisoned behind the Walls of Night.
Ravenor: In this Warhammer 40,000 series, the third book features a union of the two big villains, Zygmut Molotch and Orfeo Culzean. Either could qualify as a Magnificent Bastard, and the books hint on the friction that can develop when two MBs try to work together for extended periods.
Redwall: Happens several different times in this series, although one Big Bad is usually obviously the stronger one and the other doesn't live long. Tsarmina briefly formed one with Bane in Mossflower, Swartt Sixclaw formed one with Zigu in Outcast of Redwall, and for most of Martin the Warrior, Badrang and Clogg formed one.
The Riftwar Cycle: Happens between Belasco and Dahun in the Demonwar Saga, most recent subseries of this series. Each has his own goals and is manipulating the other to accomplish them. Both fail and are apparently destroyed, though Dahun comes a hair closer to succeeding.
Star Wars ABC's: Gets a Lampshade Hanging in this children's book, where most of the major characters get an alphabetic poem written about them. In "Z is for Zuckuss," we read: "Uh-oh, here's that bad quartet/Of bounty hunters Boba Fett/Zuckuss, Bossk and '88...."
Tales of Kolmar: For most of the trilogy the baddies are Marik of Gundar and Berys. Berys believes Marik's The Dragon, and he is the more powerful one, but Marik's more important than that and knows it. Ultimately Berys summons the Demonlord and forces him and Marik into Sharing a Body; the result is under his control but only barely.
The Thrawn Trilogy: Grand Admiral Thrawn and the insane Jedi MasterJoruus C'baoth count as this - they have a mutually beneficial alliance, but each has schemes separate from the other and plans to dispose of the other after he's served his purpose. At the trilogy's climax, they are faced simultaneously by two different sets of heroes. While in the process of carrying out their plans to dispose of each other.
The War of the Flowers: This series by Tad Williams makes this a Deconstructed Trope - it starts out with a triumvirate of main villains (fairy lords Hellebore, Thornapple and Foxglove), with Hellebore dominant because he's the one with brains, but the other two still clearly his equals, rather than underlings. Then Foxglove gets cold feet and is demoted to hanger-on, while Thornapple is still close to Hellebore's equal and perhaps the closest thing he has to a friend. By the end, Foxglove is a complete nonentity and Thornapple is a clear minion, if an important one- Hellebore is now calling all the shots.
The Spangled Mob organization in Diamonds Are Forever is controlled by two brothers, Jack and Serrafimo Spang, their based being on two different continents.
Andre and Alexis Drazen in Day 1, though they may have been acting under the orders of their father, Victor Drazen.
The German arms dealer Max, Alexander Trepkos and several other oilmen in Day 2, being the collective men behindPeter Kingsley.
Ramon Salazar and his brother Hector Salazar in Day 3. Ramon ends up killing Hector after Hector keeps interfering with his sale to Michael Amador. Amador himself and his partner-in-crime Marcus Alvers form a second duumvirate.
Debatably, President Charles Logan and Graem Bauer in Day 5.
Abu Fayed and Dimitri Gredenko in Day 6; later replaced by Cheng Zhi and Phillip Bauer. The former become a triumvirate if General Mohmar Habib is counted.
Jonas Hodges and General Benjamin Juma in Redemption and Day 7.
Briefly, Farhad Hassan and Sergei Bazhaev near the beginning of season 8.
Charles Logan and Yuri Suvarov later in Season 8 debatably
Drusilla with Spike at first and then when Angel initially did his Face-Heel Turn, there was more or less an equal partnership going on between him, Spike, and Drusilla. But, with Drusilla becoming more and more enamored with him, and Angel constantly belittling Spike for his crippled status, it soon becomes pretty clear who the alpha dog is.
Simone was this with Severin in Season 9.
Ethan Rayne was this with The First Evil in Chaos Bleeds; an odd example, as the Scoobies are technically working with him, as he chose them to be his competitors in a contest he challenged The First Evil to.
Burn Notice has Brennan and Larry teaming up in one of the finales.
In Hercules: The Legendary Journeys, several Olympian gods were dedicated to destroying Hercules. They normally worked alone, but at times, they teamed-up. In "Reunions," for example, Hera takes over Olympus with Apollo and Ares siding with her.
In Leverage's fourth season, Victor Dubenich and Jack Latimer form one. Latimer needs Dubenich's brains, while Dubenich needs Latimer's resources. The Leverage crew are able to take them down by targetting the far dumber Latimer, leaving Dubenich, a penniless ex-convict, with no way of getting at them.
Nikita: The Bigger Bad Oversight is composed of a committee, whose members appear to be equal (though Madeleine gets the most screentime, so she's arguably the leader).
It was recently revealed that Amanda is in a secret partnership/relationship with Ari Tasarov to jointly plot against their respective superiors.
Revolution: In the second half of the first season around episode 11, de facto Big BadGeneral Monroe allied with Randall Flynn, the apparent leader of the project that caused the Blackout, to secure control of the power-granting Lockets and take over the continent. Randall makes it clear that he's not subservient to Monroe, and Monroe's comments to Major Neville make it clear he's planning on turning on Randall as soon as he's no longer needed.
The Shadow Line has Commander Khokar, Commander Penney and Sir Richard Halton, the leaders of Counterpoint.
Star Trek: Deep Space Nine: During the Dominion War arc, Gul Dukat and Weyoun serve as commanders of the two halves of the Dominion fleet, and despise one another. Dukat is later replaced with his Dragon, Damar, who eventually leads Cardassia to break away from the Dominion.
Gul Dukat (and later, Damar) and Weyoun serve as Co-Dragons of the Changelings, represented by the Female Shapeshifter.
Bowser and Ganondorf have this sort of relationship in The Subspace Emissary. As one may expect, Ganondorf gets a little tired of Bowser's company. It becomes a triumvirate if Wario is included, though he rarely bothers to involve himself with his fellow "teammates".
Joker and Lex Luthor in Video Game/Lego Batman 2: DC Super Heroes
A Big Badtriumvirate is found in Oddworld: Abe's Exoddus. General Dripik of the Slig Barracks, Vice President Aslik of FeeCo Depot and Director Phleg of Necrum Mines and Bonewerkz, respectively. An inversion of The Man Behind the Man occurs, as the previous game's Big Bad, Molluck, is revealed to have been their superior.
Wild ARMs 1 has one of the most horrific inducing examples in the second half. It's Mother and Ziekfried merged as one entity. The horror is that the merging happened because Mother ate Ziekfried.
The eponymous characters in Star Wars: Knights of the Old Republic II: The Sith Lords are often called the Sith Triumvirate, although only Darth Sion and Nihulus ever work together as equals; the first third member was the Big Bad and Sion and Nihilus were her Co-Dragons and the replacement third member was never an official member of their organization. Cut content shows that Sion and Nihilus' relationship is actually a subversion, as during a deleted scene from the game that was eventually restored by modders, Darth Sion confronts Darth Nihilus aboard the latter's ship to boast about his success in "killing" the player character. Nihilus responds by forcing Sion to the ground effortlessly, and then letting him walk away humiliated; Nihilus didn't care about Sion, to the point where he considered the Lord of Pain so weak that he wasn't worth killing.
Every Fire Emblem game in the Archanea canon features Medeus and Gharnef in such a duumvirate - Gharnef specifically revives Medeus from his centuries-long death for this purpose, but it's implied he has plans which transcend Medeus and will (try to) dispose of him once he's done; for his part, since he cannot leave his castle without losing his power or risking death, Medeus relies on Gharnef to actually execute their plans for dominating Archanea.
Captains Romulus Slag and Angstrom Darkwater in Ratchet & Clank Future: Quest for Booty.
Final Fantasy XII had Venat and Vayne, who together wish to free Ivalice from Occuria's control. Venat is more like a Well-Intentioned Extremist while Vayne more appropriately fits the Big Bad role but they do work together. Venat and Dr. Cid might also qualify.
Final Fantasy XIII has Barthandelus and Orphan, who collaborate to bring about the destruction of Cocoon; however, the former of the two is given much more focus in the game itself, while the latter serves as the game's final boss.
Actually a unique example because Barthandelus and Orphan essentially fuse for the final boss.
Diablo, Mephisto, and Baal, the Three Prime Evils in the Diablo games. Diablo is the Big Bad in the first game and at least the Final Boss in the second, and Baal is the Big Bad in the expansion, while Mephisto is an intermediate boss in Diablo II, but for the plot as a whole they are equals. They seem to be loyal to each other too (well, they are brothers).
The third installment makes it explicitly clear that the Prime Evils are willing to work together so long as it suits their individual agendas, but that Hell has never really posed a serious threat to Heaven before because the Prime Evils have never been able to resist the temptation to stab each other in the back a bit too soon.
Warcraft: In the first game, Gul'dan and Medivh are this, both being responsible for the orc invasion. Also, ever since Sargeras only mostly kicked the bucket, his Co-Dragons Archimonde and Kil'Jaeden have been carrying on his crusade against life together. Until Archimonde bites it, that is, leaving Kil'Jaeden sole acting Big Bad.
Fall from Heaven reverses the usual fantasy conventions: The good gods are individually powerful but tend not to get along well, while the evil ones are all trying to twist Creation together just to make a point to the original Creator. They even run their afterlives (hells) together as a well-oiled machine to create twisted daemons, unlike the good gods whose afterlives are all disconnected.
Sarah Kerrigan and Arcturus Mengsk become this briefly in StarCraft: Brood War, until Kerrigan decides otherwise. In somewhat of a subversion, they are working with the good guys against a faction of space Nazis. By the time they return to being villains, they're at each other's throats again.
Dr. Harlan Fontaine and Leland Monroe in L.A. Noire. While Monroe runs the Suburban Redevelopment Fund's syndicite, who is the one with the ambition of making money off the city, Fontaine the mastermind behind the plans as he is the one who masterminded Courtney Sheldon's drug deals which put him in conflict with Mickey Cohen, as well as Ira Hogeboom's arson crimes.
The Eerie Voice and Malevolent Entity in Persona 4 Arena. But the Malevolent Entity wants to get rid of the Eerie Voice, which, if the theories about him being Nyarlathotep are true, would be fitting of his Complete Monster status.
Mario & Luigi: Dream Team has Bowser and Antasma, who team up to take over the island and world, as well as use the power of the Dream Stone for their own evil ends. Guess who betrays who in the end? It's not actually who you think it is.
In Jedi Outcast, the two Big Bads are a fallen Jedi named Dessan and an Imperial officer named Galak Fyyar. Both appear to be working together, but privately have different goals. In particular, Dessan wants to use the power of the Valley of the Jedi to create an army of force-sensitives with which to topple the New Republic and create an empire of his own. Fyyar has been heavily mining a rare mineral called cortosis capable of resisting lightsabers in order to be able to effectively counter Jedi and, when the time came, Dessan and his Reborn soldiers, in order to restore the Empire and rule it.
The Three Fiends, aka the Directors, from The Order of the Stick form a triumvirate. The three seem to be equal in every respect, which makes sense, since their goal is to bring an end to the fighting between their three races. They also might turn out to be the Big Bads, though they haven't got much screen time yet.
Ian and Anita in Errant Story. Both are Manipulative Bastards, and neither has any illusions about the other one's goals and objectives, but they find it convenient to work together. At least, until they don't, but by then it's too late.
During the Strex Takeover arc of Welcome to Night Vale, we have Kevin and Lauren Mallard. It's difficult to tell which one's in charge and which one isn't so it's probably safe to assume that they're both leading members of Strexcorp.
The Quintessions from Transformers, being many villains that work together and being that each has multiple personalities.
During G1's third season, the Autobots had to contend with the Decepticons and the Quintessions (who sometimes worked together to achieve their own mutually exclusive ends).
Xanatos and Demona for the first season of Gargoyles and about 1/3 of the second season. At that point their goals and methods become too divergent, and Xanatos teams up with the heroes to stop Demona from turning the population of New York to stone.
In Teenage Mutant Ninja Turtles: Fast Forward, the two main villains were invading alien Sh'Okanabo and corrupt C.E.O. Darius Dun. Despite different goals and storylines, they established a resource-sharing relationship, where Darius gave Sh'Okanabo the stolen plans for nephew Cody Jones' time window, in exchange for the assistance of the turtle clones Sh'Okanabo had created.
In the 1987 cartoon, the conventional opinion seems to be that Shredder is The Dragon and Krang is the Big Bad, but that could easily be just because The Dragon is a much better-known trope than Big Bad Duumvirate. There is no question that Shredder sees himself as a Big Bad in an equal partnership with Krang, and it usually seems as if most of the characters agree (Krang may be the only one who sees himself as Shredder's boss). And in an alternate history where the villains succeed in taking over the world, who is the natural choice for the position of Emperor? Hint: The episode isn't titled "Krangville."
In seasons four through six of The Fairly Oddparents, Anti-Cosmo, the leader of the anti-fairies, and HP, the leader of the pixies, seemed to have equal claim to the title of Big Bad. This is especially notable in season six, where the two never appeared without the other.
In season 2 of Metalocalypse, Metal Masked Assassin and Edgar Jomfru act as the season's Big Bads when they form the Revengencers, appearing in several episodes of the season. Could possibly be considered a triumvirate after they establish an alliance with Lavona Succoboso in the season finale. In a less blatant example, General Crozier and Cardinal Ravenwood could be considered the first season's Big Bad Duumvirate (with Metal Masked Assassin as their Dragon).
Big BadsVilgax and Kevin 11, respectively from season 1 and 2 of the original series, teamed up at the end of season 2 in an attempt to take the Omnitrix from Ben. Kevin's betrayal eventually caused the alliance to fail and led to both of them being trapped in the Null Void.
Later, the Forever King, Big Bad of season 4, assemble a team made of several of Ben's old enemies for the season finale while most of them weren't that much of Big Bads (guys like Clancy or Rojo had only appeared once before), the team still included Charmcaster (Gwen's Archrival) and Dr Animo (Ben's third most dangerous enemy back then).
Vilgax teamed up with Albedo in the Alien Force finale in a new attempt to take the Omnitrix. Though the alliance was successful, Vilgax then betrayed Albedo, and Ben was able to defeat him alone.
The Big Bad of the second season of Wakfu is initially set up to be Rushu, the king of Shushu until Qilby becomes another Big Bad of the season and the two team up.
In Book 2 of The Legend of Korra, it is possible that Vaatu and Unalaq were this rather than Unalaq being The Dragon to Vaatu. While Vaatu was far more powerful than Unalaq, he was largely helpless for most of the season until Unalaq's machinations allowed him to escape, and Unalaq did so out of his own ambition rather than any loyalty to Vaatu. This comes across most strongly in the finale, where they merge into the Dark Avatar and are treated as a single threat, rather than Vaatu overriding Unalaq (or the other way around) like most similar situations.
Book 2 of Avatar: The Last Airbender also ended this way, with Princess Azula and Long Feng teaming up to perform a coup on the Earth City capital, Ba Sing Se. However, from the beginning both were planning to betray the other with Azula planning to take it for the Fire Nation and Long Feng planning to take control from the Earth King and have a more iron-fisted ruler for the Earth Kingdom. When the coup is complete, Azula turns his own men against him, having impressed and terrified them with her ruthlessness and cunning, ending it with a Breaking Speech.