Lex Luthor is the main antagonist of the DC Animated Universe. He debuted as the overall main antagonist of Superman: The Animated Series, he later returned as a major antagonist in Justice League and Justice League Unlimited. He was a billionaire and a criminal mastermind. He also was one of the most brilliant minds of the Earth and one of Superman's greatest foes.
Superman: The Animated Series
Lex Luthor is the founder and CEO of LexCorp. He grew to resent Superman when he stole his spotlight as Metropolis' savior, and usually invested heavily in some of the Man of Steel's greatest foes, such as Metallo and Livewire. He sought to kill Superman for shutting down his major operations and costing him a lot of money. Although Superman already put away many of Luthor's co-conspirators, he could never convict Luthor himself due to lack of evidence. He was also known for his betrayals on many associates, causing many to leave LexCorp; the only one left was Mercy Graves. Lex also is shown to hate Batman as well, as he is an intellectual rival who teamed up with Superman to fight him when he and Joker teamed up, preventing Superman from being killed by Joker's kryptonite in the process. In Legacy, he was thrilled, the whole world turned against Superman when Darkseid brainwashed him and let him loose to take over and invade Earth. But Superman snapped out of it and earned the world's trust back and dismissed the charges against him.
Luthor later fought the Justice League, but was subsequently defeated, exposed as a crook, and sentenced to prison. He also learned that he had a form of radiation poisoning as a result of carrying around a chunk of Kryptonite for years, leaving him with only a few more months to live. He then joined up with Cheetah, Star Sapphire, Shade, Copperhead (who would be in jail and replaced by the Joker), Solomon Grundy and Ultra-Humanite, forming the Injustice Gang, in an attempt take down the Justice League, but failed. Luthor later "redeemed" himself by aiding the Justice League in defeating the Justice Lords and was given a full pardon.
Justice League Unlimited
After being freed from prison and cleared of all charges, Luthor reestablished his company and later entered politics and ran in the U.S. Presidential Elections. However, still bent on destroying Superman, he created Project Cadmus and succeeded in ruining the Justice League's reputation twice: once by causing Superman and Captain Marvel to fight each other, causing great destruction in the city, and again by taking control of the Watchtower's orbital cannon and causing it to fire on a Cadmus-related building in New Mexico.
Luthor's malevolent plans were later exposed by Batman and the Justice League, only for Brainiac to reveal that he had been dormant inside Lex ever since the episode Ghost in the Shell. Luthor later convinced Brainiac to fuse with him because they both could reach their ultimate goals. He then battled the Justice League, proving to be one of the group's most difficult foes. However, the Flash was able to separate the two after tapping into the Speed Force.
Luthor went back to jail with a damaged psyche. After Luthor escaped prison again thanks to The Key, Gorilla Grodd offered him membership in the newly formed Legion of Doom. Joining only to revive and refuse with Brainiac, Luthor eventually overthrew Grodd and took over the Legion (who did not oppose him after they learned Grodd's ultimate plan was to turn humanity into apes). Eventually, Lex's quest to revive Braniac lead the Legion into space, where he found a version of Brainiac that had been destroyed years earlier. However, Tala freed Grodd and he and a faction of the Legion fought Luthor and his supporters (which included the likes of Giganta, Bizarro, Toyman, Sinestro, Cheetah, Star Sapphire, Evil Star, etc.) After killing Grodd and trapping and absorbing Tala's magic to resurrect Brainiac, Lex discovers that he had accidentally resurrected Darkseid instead.
Luthor and the rest of the surviving Legion members barely escaped from Darkseid and made their way to Earth, where Luthor warned the Justice League, and he and his allies reluctantly team-up with them to fight against Darkseid and his army. Before the battle against Darkseid, Luthor points out to the Justice League that he doesn't want to help them save the world, but get revenge on Darkseid for destroying Brainiac and ruining his plans, before he and the Justice League go back in being enemies again as usual. He later left the battle with Metron and discovered the Anti-Life Equation. Returning to Earth with the Equation, he offered to share the knowledge with Darkseid, and they both disappeared in a spark of light. While they are presumed dead by the public, members of the Justice League have theorized they will eventually return yet again. However, it was revealed that both Luthor and Darkseid are now part of the Source Wall, that is the fate that occurs to all creature that solved the Anti-Life Equation, like them.
- Clancy Brown later reprised his role as Luthor in Lego Batman 2: DC Super Heroes and in Lego Batman 3: Beyond Gotham.
- His fusion with Brainiac is a reference to an idea that film director Tim Burton had for his unmade Superman Lives film. According with Burton's idea, Brainiac and Luthor would merge and became a creature named Lexiac.
- Although both Luthor and Darkseid's fate are left unexplained in the series, show's late writer Dwayne McDuffie explained in his own website that Luthor and Darkseid are now part of the Source Wall because they solved the Anti-Life Equation. It's completely unknown if this means that they are dead or not.