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.
- Any crossover featuring Alien is sure to include this if there's an interesting species for the xenomorphs to get their facehuggers on.
- Alien/Vampirella includes vampiric xenomorphs.
- 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.
- Batman/Aliens 2 includes Xenomorphs fused with five members of Batman's Rogues Gallery: Joker, Poison Ivy, Two-Face, Scarecrow, and Mr. Freeze.
- Mortal Kombat X's playable Xenomorph is born from a Tarkatan (Baraka's race).
- Due to the nature of it, every villain in the Amalgam Universe counts in one way or another.
- Batman/Judge Dredd: Die Laughing has the Dark Judges recruiting and empowering The Joker, giving his laugh the ability to pop heads.
- Star Trek: The Next Generation/Doctor Who: Assimilation² features a combined force of the Cybermen and the Borg.
- Freddy vs. Jason vs. Ash has Freddy Krueger getting the Necronomicon ex Mortis and using it to wreak havoc.
- 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.
- 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.
- 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.
- Aliens vs. Predator: Requiem features the Predalien, a creature combining both titular extraterrestrials and being more of a threat than either.
- 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.
- 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.
- 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.
- In Power Rangers: "Reinforcements from the Future", the two-part crossover between Time Force and Wild Force, there are 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.
- In Mario + Rabbids Kingdom Battle, many bosses are Rabbids mixed with something from the Super Mario franchise due to a Merging Machine mishap.
- Marvel vs. Capcom: Infinite:
- 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 Einst Regisseur pull the same trick, fusing with the White Star into a new unique form.
- Euzeth Gozzo is especially fond of this trope, using it in two of his three appearances as the lead villain across the franchise's history. His concoctions invariably lead to a machine that looks like himself as an Ultraman.
- 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.
- 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.