Ultraman is the name of several fictional characters, who are supervillains that appear in stories published by DC Comics. The characters are all evil criminal counterparts of Superman. Ultraman first appeared in Justice League of America #29 (Aug. 1964).
Unlike Superman, the Earth-Three Ultraman gets stronger every time he is exposed to kryptonite, originally developing a completely new superpower with each new exposure. In one such encounter, Ultraman acquired the ability to see through dimensional barriers, thus alerting the Crime Syndicate to the existence of alternate Earths in their first appearance. This allowed the Syndicate to attack the Justice League and Justice Society. Ultraman also differed from Superman in that his version of Krypton had not exploded. Where the Kryptonite came from is unknown.
In the early 1980s, Ultraman teamed up with Lex Luthor of Earth-One and Alexei Luthor of Earth-Two in an unsuccessful attempt to eliminate the Supermen of Earths-One and -Two (the Supermen were, in turn, assisted by the heroic Alexander Luthor of Earth-Three). Later, Ultraman joined the rest of the Crime Syndicate in a teamup with a time-traveling villain named Per Degaton in his attempt to conquer Earth-Two, but this proved unsuccessful as well, and the events were wiped from the timeline afterwards. The original Ultraman was eliminated in the 1985 12-issue limited series Crisis on Infinite Earths. Distraught at the fact that his superpowers were useless at the one time he actually needed them, he flew straight into the anti-matter cloud that was destroying Earth-Three, telling Power Ring "I do what I have done all my life. Fight... to the very end!"
Duplicates of the Pre-Crisis Ultraman showed up in the pages of Animal Man. There he learned that he was seemingly a comic book character himself, who existed only for the entertainment of others. He also fought against a more homicidal version of himself, who wished to kill, seemingly for the sake of killing. This Ultraman later faded into the mask of the Psycho-Pirate, who, for a time, was the only one who remembered the Pre-Crisis universe.
Other copies of the Pre-Crisis Earth-Three Ultraman have made appearances most recently in Infinite Crisis where Alexander Luthor, Jr. wanted to create so called perfect beings out of his models of long dead father Alexander Luthor, Sr. the lone super-hero of Earth-Three, Superman (both of Earth-One and Earth-Two), Wonder Woman of Earth-One and Two) and the Earth-Three Ultraman and Super-woman.
Unlike the original Pre-Crisis Earth-Three dimensional Kryptonian Ultraman, the antimatter Ultraman was fully rewritten for modern continuity as Lieutenant Clark Kent, a human astronaut from the antimatter Earth and no longer an alien matching Superman exactly. After a fiery space shuttle crash, an unknown alien race (possibly Kryptonians) reconstructed Kent in an attempt to repair the damaged astronaut, which ended up altering the human both mentally and physically, giving him ultrapowers similar to Superman's superpowers. According to Alexander Luthor, the process also twisted Ultraman's mind. In contrast to Superman, Ultraman's power relies on his proximity and exposure to a substance called Anti-Kryptonite; the longer and farther he is separated from it the weaker he becomes. This substance has repeatedly been shown to have no apparent effect on Superman as Kryptonite has been shown to have no effect on antimatter Clark Kent's superhuman powers and abilities.
Antimatter Ultraman is married to his Crime Syndicate teammate Superwoman; at least in the identity of their alter-egos, Clark Kent and Lois Lane. In the early 2000s, the two had a child together. However, Superwoman maintains a periodic affair with another member of the Crime Syndicate, Owlman, much to Ultraman's frustration.
However, after the Kandor residing in the fortress was revealed as a fake (in Superman #670), it was destroyed and its various citizens exiled.
Antimatter Clark Kent has been shown to have returned to his source Earth and is again leading the antimatter Crime Syndicate. The antimatter Crime Syndicate is currently shown to be kidnapping people from all 52 matter universes to attempt to repair their Earth after the destruction done by the Weaponers of Qward as shown in the Trinity series.
According to the recent events of "Final Crisis - Superman Beyond", antimatter Clark Kent was shown to be in the DC Universe's version of Limbo, along with several other alternate universe Supermen, including Kal-El.
While this Ultraman wears a close Earth-3 version of the costume, with long red gloves, red boots, and the same base shield of Superman with the point down (as opposed to the gloveless costume of JLA: Earth 2 that wore boots incorporated into his costume, and had nodules of anti-kryptonite accenting various parts of it so as to maintain his powers), the character is described in the verbage above his logo as being "Lt. Clark Kent" from the Anti-Matter universe. This second Ultraman is shown to be fundamanetally different from the first one as he is shown to be powered by New Earth's Kryptonite and was being changed to operate on Earth's yellow sun and drained by red sun radiation same as Superman, in the same way that Sir Mixyezpitelik was being changed to act like his matter based counterpart Mxyzptlk. This is fundamentally different from whenever the first antimatter Clark Kent has come into matter based reality of the Justice League who continues to operate on anti-Kryptonite and maintain his personality intact.
When the Earth-3 Ultraman is shown in later appearances of the Countdown series he is no longer aged but young. It is unclear if the old Ultraman of 52 issue 52 is a separate person or the same one. If the two are separate, that would fit with the idea of Superman having a superpowered successor in his younger cousin Supergirl/Power Girl. At present this is not clarified. Based on comments by Grant Morrison, this alternate universe is not the pre-Crisis Earth-Three, making this a new character unrelated to previous versions. The name of this Earth-3 team has been revealed to be the Crime Society of America. The Society make their first solo appearance in Countdown Presents The Search for Ray Palmer: Crime Syndicate #1 written by Sean McKeever and illustrated by Jamal Igle. In subsequent appearances, the Crime Society are agents of Monarch's Multiversal army. Presently the matter based Earth-3 Ultraman is missing and presumed dead along with most of the major members of the Post Crisis Earth-3 Crime Society who joined the Monarch Army.
Presently NONE of the true Ultramen have met with other versions of themselves i.e., antimatter Clark Kent has not in panel mentioned or been shown to have interacted with the Ultraman of Post Crisis Earth-3 before the Ultraman of Post Crisis Earth-3 was apparently killed in the Countdown series, nor with the second antimatter Ultraman of the Brave and the Bold series. It remains to be seen if any of the different versions of Ultraman will meet up in the coming episodes of the DC publications.