When one creates a crossover, the issue of who the villain of the event should be comes up. Should it be a villain from one of the involved properties, a team-up, or something new altogether?
Sometimes, the best solution is to combine stuff from the crossing over universes to make a villain appropriate to both. Thus, the Crossover Combo Villain. It could be a character from one work utilizing an element from the other, a literal fusion of characters to create a single new antagonist, or something else entirely— so long as it combines elements from the involved works into a single antagonist, it qualifies.
Note that just having an original villain for a crossover doesn't count, they have to combine elements from the works crossing over in some way.
Contrast Crossover Villain-in-Chief, which sees an already established villain rise to lead the forces of evil.
Examples:
- The Rave Master/Fairy Tail crossover OVA has minor Fairy Tail villain Klodoa operating an augmented Jackpot powered by a Dark Bring.
- Super Robot Wars Original Generation The Inspector, an adaptation of Super Robot Wars: Original Generation 2, plays with some of the original's crossover elements (see the videogames section below).
- The Stern Regisseur encounter splits the difference between its portrayals in OG2 (where it is a fusion between the Einst commander Neue Regisseur and the OG1 villains' space station White Star) and the OGs remake (where it is simply the commander's normal appearance and the station remains unscathed) - its design is changed from a giant spherical Neue Regisseur to simply Neue Regisseur attached to the White Star by a stalk, allowing it to be destroyed while leaving the station largely intact.
- The Einst also manage to corrupt secondary antagonist Wendolo of the Inspectors into a Mole for their cause, granting his mecha a more organic form - something which doesn't occur in either videogame version of the story.
- Due to the nature of it, every villain in the Amalgam Universe counts in one way or another. That nature also means there's Crossover Combo Heroes to fight them.
- Batman/Judge Dredd: Die Laughing has the Dark Judges recruiting and empowering The Joker, giving his laugh the ability to pop heads.
- Batman/Teenage Mutant Ninja Turtles:
- In the first miniseries, Batman's Rogues Gallery are exposed to Teenage Mutant Ninja Turtles mutagen, turning them into mutants.
- In the third miniseries, Krang merges Batman and the Ninja Turtles' multiverses, resulting in an unstable Merged Reality where the heroes and villains are either merged or share an origin. In the case of the bad guys, the Foot Clan and Batman's Rogues Gallery are all merged into the Smile Clan, its members including a Rocksteady-esq Clayface, a Killer Croc-Bebop, Deadshot as a random elite soldier, Harley Quinn takes over Karai's role as The Dragon and The Shredder is replaced by the Joker as The Laughing Man. That is until Oroku Saki suddenly remembers who he is, becomes the Shredder again and throws the Laughing Man into a vat of chemicals.
- Star Trek: The Next Generation/Doctor Who: Assimilation² features a combined force of the Cybermen and the Borg.
- In JLA vs. Predator, the villains are a group of genetically modified Super Predators that each utilize powers similar to that of a specific JLA member.
- Both of the IDW Infestation events utilize this trope in various ways. Examples include zombie Transformers, a zombie Mr. Stay Puft, and more.
- In the Power Rangers Crisis Crossover Shattered Grid, Lord Drakkon gathers morphers from many different Power Rangers teams to augment his own powers with theirs.
- He-Man/ThunderCats has Skeletor and Mumm-Ra absorb the Ancient Spirits of Evil and combine to form Mumm-Ator.
- Worlds Collide and Worlds Unite combine many elements from Sonic and Mega Man, as well as other involved franchises in the latter. Standouts include the Chaos Devil, Robot Master versions of Sonic characters, and Sigma drawing power from the entire multiverse.
- The final issue of the IDW Hasbro crossover Revolution (2016) sees Baron Karza fuse himself with a horde of Dire Wraiths into a more monstrous form.
- When the Lunaverse collides with the canon MLP:FiM universe in Crisis On Two Equestrias, the two Princess Protégés must tangle with The Dark & Omnipotent Antithesis, a being created from the combined animosity between Representative Trixie Lulamoon and the future Princess Of Friendship, as well as both parties' respective animosities with the other's counterparts in their own worlds,note brought to life by the two worlds' Elements Of Magic.
- Flashpoint 2: Advent Solaris turns Mephiles the Dark into one, as not only is he a Sonic character but he also is revealed later on to be a union of Darkseid and Trigon.
- The Big Bad of the Gravity Falls/Soul Eater crossover Gravity Soul is a fusion of Bill Cipher and Asura after they come Back from the Dead.
- Eventually happens in The Miraculous Adventures of Dan Kuso when the Big Bad, a Gundalian takes in an Akuma and then does a Fusion Dance with an army of Bakugan to attain his One-Winged Angel form.
- Code Prime: While antagonistic Geass users have been a thing in the original series, it's when Megatron grants himself a Geass of his own that he becomes the first Cybertronian to do so. There's also the fact that the corruptive influence of Geass (in this universe) originates from Unicron himself.
- The Mountain and the Wolf: Several Westeros natives join the Wolf, and receive Chaos mutations or gifts in return:
- Jaime Lannister's gold hand is infused with a daemonic entity that responds as his real hand did and turns it into a Morph Weapon.
- Theon Greyjoy gets turned into a Champion of Chaos.
- The Iron Fleet are described as having various mutations such as tentacles.
- Qyburn doesn't get any mutations, but he does work on something involving dead bodies, and later is given access to the Skaven and their Lightning Can Do Anything technology.
- An Ironborn is introduced to the cult of Khorne, and goes around villages in Westeros teaching people to fight back against their enemies and inducting them in the cult.
- Gregor Clegane, Ramsay Bolton, Petyr Baelish and Euron Greyjoy return as hideously mutated champions of Chaos.
- Tales of Kitty-Whiskers and Ladybug:
- Played With for the story's akumas. The majority of them are various characters from Ace Attorney but with the exception of Daryan all of them are normally heroic or just the regular crazy civilians like Wendy Oldbag.
- The story's version of Hawkmoth is revealed to be Kristoph Gavin, the Big Bad of Apollo Justice: Ace Attorney and Apollo's boss.
- In Teen Titans Go! vs. Teen Titans, 2003 Trigon and 2013 Trigon merge into a being known as Hexagon.
- An in-universe example happens in Wreck-It Ralph, where the Big Bad Turbo jumped from his racing game Turbo Time into the kart racer Sugar Rush and made himself into its ruler, King Candy. Later, when the Cy-Bugs from the shooter Hero's Duty invade, Turbo gets eaten and absorbed by them, his final form being a mashup of his Turbo and King Candy personas with a Cy-Bug.
- Kamen Rider:
- Kamen Rider Kamen Rider OOO & W Featuring Skull: Movie War Core ends with the two main Riders facing off against Kamen Rider Core, the incarnation of all Kamen Riders' memories created from the Memory Memory and Nobunaga's black Core Medals combining.
- The first two movies for Kamen Rider Ex-Aid, about doctors fighting bio-digital video game viruses, licensed appropriate Bandai Namco Entertainment arcade games to serve as the virus of the week. Kamen Rider Heisei Generations, co-starring Kamen Rider Ghost (who is Exactly What It Says on the Tin), features Pac-Man and Kamen Rider × Super Sentai: Chou Super Hero Taisen, co-starring the Space Opera Uchu Sentai Kyuranger, involved Xevious.
- Sadako vs. Kayako ends with the creation of Sadakaya, a fusion of Sadako and Kayako possessing the body of the living Yuri.
- Super Sentai:
- Mirai Sentai Timeranger vs. GoGoFive: The final enemy is BoriPierre, a Fusion Dance between the film's Timeranger-based Monster of the Week Boribaru and Kyūkyū Sentai GoGoV supporting villain Pierre.
- By accident or design, the name scheme developed for the monsters of the week in Juken Sentai Gekiranger gave rise to one for the crossover movie Engine Sentai Go-onger vs. Gekiranger. A kung-fu fighting cyborg turtle, fitting both the rival martial arts school of Gekiranger's villains and the cyborg/mechanical theme of Go-Onger's. All because the already developed naming theme note turns Kamenote into Meka.
- In commemoration of the franchise's 45th anniversary, Kikai Sentai Zenkaiger the Movie: Red Fight! All Sentai Great Assemble!! has Super Warumono World, whose body is composed of elements from all 44 of the previous Sentai Big Bad.
- Every Monster of the Week in Avataro Sentai Donbrothers is an homage to a previous Super Sentai series. With every series mandated to have a crossover film with its immediate predecessor, the monster themed after Donbrothers' predecessor Zenkaiger was naturally reserved for that film.
- Super Sentai and Kamen Rider crossovers:
- The villains in Kamen Rider × Super Sentai: Super Hero Taisen have the Combining Mecha Big Machine, formed from the flagships of the antagonist groups of Kaizoku Sentai Gokaiger and Kamen Rider BLACK RX.
- The Co-Dragons in Kamen Rider Saber + Kikai Sentai Zenkaiger Super Hero Senki are a Kamen Rider Saber Monster of the Week who is an Evil Knockoff of Kikai Sentai Zenkaiger's protagonist Zenkaizer and a Zenkaiger Monster of the Week who is an Evil Knockoff of the titular Kamen Rider Saber. It also has a Crossover Combo Hero, as for their finishing move on the Big Bad, Saber and Zenkaizer perform a Fusion Dance into an one-off form for Saber with Zenkaizer's color scheme.
- The titular protagonist of Kamen Rider Decade is an odd heroic inversion of the trope, acting as a villain to all previous Riders with the ability to transform into them.
- When Decade's dimension hopping adventures landed him in the world of Samurai Sentai Shinkenger, the main antagonist of the story turned out to be a Shinkenger Monster of the Week that stole the Diendriver, becoming a monstrous Kamen Rider. This power up also disabled the standard Sentai monster ability to turn into a giant, so Decade wouldn't be left behind by the obligatory giant robot fight.
- Similarly, Kamen Rider Zi-O features the titular Rider's evil future self, Ohma Zi-O, as the nigh-omnipotent ruler of the world, who's defeated every other Kamen Rider and has complete mastery of all of their powers. He's so powerful that actually defeating him in battle isn't even entertained as an option, with the overall goal of the season instead being to prevent him from existing in the first place.
- In Power Rangers: "Reinforcements from the Future", the two-part crossover between Time Force and Wild Force, has the "Mut-Orgs" - a group of surviving Orgs who were unsealed by Ransik in the year 3000 and used his mutant DNA to construct new, more powerful bodies for themselves.
- Worlds Collide: Battle for the Multiverse, a Crossover between Renegade Game Studios's Essence20 Hasbro Tabletop RPGs, features Lord MindWaveZ, a fusion between Shockwave, Doctor Mindbender, and Lord Zedd created when the three of them simultaneously tapped into a network of multiversal energy.
- Transformers:
- Generation One Starscream has become this trope thrice:
- In the prose short stories accompanying the Transformers × Neon Genesis Evangelion toys, the Autobots must team up with NERV to stop "Angelscream", an Angel possessed by his ghost.
- In the Mazinger Z Versus Transformers manga, he absorbs photon power and Mazinger Z's spare parts at the climax, becoming "Mazinscream".
- Though Starscream becoming an undead ghost is a pre-existing recurring concept in Transformers fiction dating back to The Transformers, Transformers/Ghostbusters employing it is this to give Ghostbusters (IDW Comics) a valid reason to get tangled in the affairs of giant alien robots from outer space.
- Transformers vs. the Terminator: At the end of the miniseries, Skynet becomes this after the Terminator it sent back in time succeeded in his missions to ensure its creation and cripple the Transformers. Whereas the original timeline was an Evil Versus Evil war between Skynet and the Decepticons, the new timeline has mankind reverse-engineer the corpse of Megatron, whom the Terminator killed in the past, into Skynet.
- Generation One Starscream has become this trope thrice:
- In Mario + Rabbids Kingdom Battle, many bosses are Raving Rabbids mixed with something from the Super Mario Bros. franchise due to a Merging Machine mishap.
- Marvel vs. Capcom: Infinite: Ultron and Sigma combine to form Ultron-Sigma.
- Mortal Kombat vs. DC Universe features Dark Kahn, a fusion of Darkseid and Shao Kahn.
- Super Robot Wars is heavy on this, given that most titles feature a Big Bad Ensemble. The final boss is usually either a powerful alien, a godlike entity, or a particularly resourceful human whose robot uses all of the combined technology from the shows involved in the game.
- Games featuring the Devil Gundam often replace its gigantic final form by having it fuse with a different artificial satellite from another series (such as the Axis, producing the "Devil Axis").
- Original Generation 2 has the Einsts' leader Neue Regisseur pull a similar trick to the Devil Gundam, fusing with the derelict White Star (the villains' orbital battlestation from Original Generation 1) to achieve a new One-Winged Angel form called "Stern Regisseur". This is however Retconned by Original Generations, where the encounter uses the Stern Regisseur design from the start and there's no indication of it fusing with anything.
- Super Hero Sakusen: Euzeth Gozzo gathers data from the heroes to create "Choujin Zest", a Humongous Mecha resembling a winged Ultraman version of himself which serves as the Final Boss.
- 2nd Super Robot Wars Original Generation:
- Euzeth Gozzo (who can remember past iterations of the universe) combines elements of his previous plans by collecting various defeated enemy units, feeding their data into the Mechanical Abomination AI-1, then having it simultaneously absorb the angelic Nashim Gan Eden, a Cross Gate, and Ing (see below) to create the blasphemous "Adamatron",note which resembles a giant limbless Fallen Angel with Euzeth's mask as its face.
- Player Character Ing is revealed to be not just one of the augmented Machinery Children, but one created from the DNA of the Alpha continuity version of Euzeth's favoured pawn Ingram Plissken (Machinery Children do exist in the Alpha setting, but only in a Bad Future).
- Super Robot Wars EX: The Final Boss of Masaki's route is the "Super Masouki" Duraxyll - a Masouki (a spirit-powered mecha from the Magical Land of La Gias) which incorporates data from various Gundams into its design, including a Chest Blaster similar to the ZZ Gundam's High Mega Cannon, and remote weapons similar to the Nu Gundam's fin funnels. When the Duraxyll reappears in the Original Generation continuity it uses data from the Huckebein series instead, resulting in a slightly different appearance with a less Gundam-like head.
- Mazinkaiser debuted in Super Robot Wars F Final as a Crossover Combo Hero created when Mazinger Z was exposed to large quantities of Getter Rays; later appearances remove this and make it simply a Super Prototype. Similarly, Super Robot Wars V introduces Mazin Emperor G as an upgraded Great Mazinger fuelled by both Photon Power and Getter Rays, designed as a countermeasure in case either of the two ever spawned something out of humanity's control (making it a Suspiciously Similar Substitute for Great Mazinkaiser from Shin Mazinger ZERO).
- Super Mario Bros. Z features Captain Basilisx, a high-ranking Koopatrol that was given tremendous power and stone-gaze ability thanks to the serum made by Dr. Eggman.
- In Ben 10/Generator Rex: Heroes United, the villain is Alpha, a nanite-based entity from Rex's universe who eventually steals the ability to transform into some of Ben's alien forms.
- The Ben 10: Omniverse episode "T.G.I.S.", a crossover with The Secret Saturdays, has Dr. Animo revive V.V. Argost as a patchwork of aliens and cryptids.
- In The Grim Adventures of the KND, the Delightful Children from Down the Lane, Billy, Grim's scythe, and Billy's dad's lucky pants get fused together in a newly rebuilt Delightfulization Chamber, resulting in the creation of the Delightful Reaper. It’s rampage doesn’t just include their shows; other then-current Cartoon Network characters are shown to have been assimilated at some point, popping out of the Reaper only briefly when it’s defeated.
- The second and third The Jimmy Timmy Power Hour both include these, the former having a fusion of Professor Calamitous and Jorgen von Strangle, and the latter featuring Shirley, a villain custom-made by Jimmy and Timmy to challenge them.
- Any crossover featuring Alien is sure to include this if there's an interesting species for the xenomorphs to get their facehuggers on.
- Aliens vs. Predator: Requiem features the Predalien, a creature combining both titular extraterrestrials and being more of a threat than either.
- Alien/Vampirella includes vampiric xenomorphs.
- Batman/Aliens has a Xenomorph spawned from a caiman, while 2 includes Xenomorphs fused with five members of Batman's Rogues Gallery: Joker, Poison Ivy, Two-Face, Scarecrow, and Mr. Freeze. The Big Bad is defeated when the sixth one which fused with Killer Croc is completely animalistic and shows none of the biological restraint to not kill her as with the other five.
- Mortal Kombat X's playable Xenomorph is born from a Tarkatan (Baraka's race).
- In Superman/Aliens and its sequel, the primary threat is the imminent birth of Kryptonian-born xenomorphs in the first, and New God-born ones in the second.