Ultron is a classic Avengers villain and one of the greatest superheroes in Marvel Comics. He's even more intriguing considering that the Avengers actually created him. The brainchild – literally – of Dr. Hank Pym turned on his creator and has made life pretty hard for everybody in the ensuing decades since his debut back in 1968. Along the way, he has continued to evolve and adapt.

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The key feature of Ultron is his ability to progress. Endless versions of the characters emerge every so often, providing the Avengers (and usually everyone else) with massive headaches, but comic book fans with lots of joy.

10 Ultron-1

Ultron Avengers

Ultron-1 was an early example of a retcon. The first Ultron fans meet is Ultron-5 in the pages of Avengers #54 in 1968. It's only in a flashback that readers learned that Ultron was actually the creation of Hank Pym, also known as Ant-Man, and just a guy who maybe needs to stop doing things.

Ultron-1 was a very simple robot on treads with a very basic body. What he did have were all of Pym's thought and memory engrams. These allowed Ultron to quickly evolve into the terrifying and murderous machine he would eventually become.

9 Crimson Cowl

Crimson Cowl Ultron

The Crimson Cowl isn't really a different version of Ultron, but one of the first. The debut of the character in 1968 involved some complicated sleight of hand involving not just Ultron, but his own subsequent creation, the Vision.

Ultron skulked around under a heavy red cloak under the name Crimson Cowl until he revealed himself and his true origin. It would be the last time that Ultron would be shy about who and what he was in just about every medium the character appears in.

8 Ultron-5 (Earth's Mightiest Heroes)

Earth's Mightiest Heroes Ultron-5

One of the more interesting visual takes on Ultron in other media belongs to the animated series Avengers: Earth's Mightiest Heroes, one of the best cartoons on the super-team out there. This version of Ultron kept very close to the original comic book, right down to the Kirby crackle in his always open mouth.

One major design difference in the cartoon was the addition of red glowing panels on his upper chest and shoulders. This version of the character condensed quite a bit of Ultron history into his animated arc.

7 Ultron-13

Daredevil vs Ultron Acts of Vengeance

In the early '90s, Ultron had reached his thirteenth iteration. It would become one of his most unique. John Romita Jr. designed this take on the android villain, which debuted in the pages of Daredevil of all places. Ultron-13 was a far boxier and larger version than the previous ones, with a very thin waist that looked and moved almost like an accordion.

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Ultron-13 would continue to evolve visually in later appearances, though he would keep his number designation for a while (there were about to be a lot more of him though).

6 Ultron Unlimited

Ultron George Perez

Iconic comic book artist George Perez, behind some of the greatest Teen Titans stories ever, got a couple of cracks at Ultron. The second took place in the '90s, with the Ultron Unlimited saga. In this story, Ultron goes nuts with alternate versions.

It's not just Ultron-15 that debuts in this story, but hundreds of others, all the way up to Ultron-458. All the variations allowed Perez and the other artists that followed some flexibility in presenting the character. One such variation was an Ultron with a green energy glow in his mouth and eyes as opposed to the signature red.

5 MCU

Ultron mcu Cropped

Ultron is a major Avengers supervillain and it was only a matter of time before he showed up in the big-screen franchise. Ultron crashed into the MCU in a big way in Avengers: Age of Ultron, setting off a chain of events that would really only resolve several films down the line.

This version of the character features a vibranium exoskeleton instead of an adamantium one, and a mandible mouth which maybe didn't quite make sense. His evolving design in the movie was in keeping with his comics roots, though it was Tony Stark who created him on screen and not Hank Pym.

4 Gold Ultron

An image of Ultron fighting the Avengers, holding off Iron Man and Captain America in Marvel Comics

The Age of Ultron is one of Marvel Comics' many dystopian alternate universes. This one follows in the footsteps somewhat of stories like the Age of Apocalypse by imagining a world in which Ultron took control. Ultron created an army of Ultron drones (like the movie it later inspired) and decimated humanity.

Ultron evolved in this story into a new gold form, by far his most powerful and most terrifying iteration yet. The time-traveling effort to destroy him actually created a new, even worse timeline, something that may or may not be occurring in the MCU post-Endgame.

3 Ultron-8

Ultron surrounded by red smoke

Ultron was a fantastic villain for the early Marvel Universe because of his tenacity. He was an all-time villain because he took advantage of what is now a trope – endless resurrections – and made it part of his character. Ultron-8 debuted in 1977 with a shinier, spikier design courtesy of legendary artist George Perez, well-known for his work on the epic DC event Crisis On Infinite Earths.

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This version of the character took the Frankenstein theme to new levels. He created his would-be bride, Jocasta, who Hasbro just memorialized in plastic as a Marvel Legends action figure for the first time ever.

2 Ultron-6

Ultron Avengers

The early versions of Ultron were great, taking a fantastic original design from John Buscema in Avengers #54 through Avengers #58 and slowly refining it. Those early versions clung pretty hard to the concept of a robot, though, and it wasn't until Ultron-6 debuted in 1969 that the character really started to separate himself from the mutant pack.

This version coated his entire body in adamantium (the movie version went with vibranium because, well, it was a whole thing). Ultron also becomes much more menacing thanks to small design changes in his face.

1 Ultron-Phalanx

Phalanx Ultron Sitting on his Throne

Ultron is one of the most terrifying villains in the Marvel Universe, but he's far from the only artificial intelligence that represents a threat to mankind. The Phalanx represents perhaps a greater one, as the X-Men well know.

Somehow the Marvel Universe continued to exist after Ultron and the Phalanx combined. Ultron merged with the alien techno-organic species in the aftermath of the Annihilation Conquest event and created his most advanced and most lethal version ever. It was only with some truly cosmic intervention that he was defeated.

NEXT: Marvel: 5 DC Villains Ultron Would Team Up With (& 5 He Would Hate)