Tomorrow Woman was one of the most memorable elements of Grant Morrison's acclaimed run of JLA, despite her being killed off as quickly as she was introduced. Her introduction stands as one of the series' most landmark issues, personifying the neoclassical premise of the run. While Tomorrow Woman's time with the Justice League was brief, she went on to appear in other comics and universes, and here's the story behind the psychic android and why her sacrifice made her one of DC's most tragic but heroic characters.
Tomorrow Woman
Created by Grant Morrison and Howard Porter, Tomorrow Woman debuted in JLA #5. She was created by robotics experts Professor Ivo and T. O. Morrow, who had both vexed the Justice League in the past with their mechanical creations. They made the android heroine with the idea that she would infiltrate the Justice League. Once instructed, she would detonate an EMP device inside of her that would take out the JLA when they least expected it. This was all kept from Tomorrow Woman, who believed herself to be merely a metahuman with psychic powers.
Joining the League when they had a membership drive, she quickly gained the trust of every member. Her moments quickly became numbered when the League faced IF, a powerful weapon from the future. She soon realized that only an EMP would destroy the weapon, but she fought against activating it and killing her teammates. Instead, she took on IF directly, activating the EMP away from others. This not only killed IF, but Tomorrow Woman as well. Elsewhere, T.O. Morrow reveled in the fact that he created an advanced android capable of having independent thoughts beyond its programming. Capturing Morrow and Ivo, Superman and the League mourned Tomorrow Woman as truly one of their own.
Trinity
This wasn't the end of Tomorrow Woman, as she gained immense popularity in her brief existence. Her next appearance was JLA: Tomorrow Woman, which expanded on the events of her sole appearance. Her characterization was also fleshed out to make her more cynical as she questioned the Justice League's heroism.
She showed up next in the Hourman series, which starred an android Hourman from the future. He used his own time manipulation powers to briefly revive Tomorrow Woman for an hour, but she only wanted to use the extra time to save as many people as she could. This impacted Hourman's worldview, causing him to deeply mourn her loss when the hour was over.
Her only other major appearance was around the middle of the 52-week series Trinity. This version of the character was on a separate Earth that was defended by the Justice Society International. This world's Trinity wasn't made up of Superman, Batman and Wonder Woman, but instead Tomorrow Woman, Green Arrow and Black Adam.
Tomorrow Woman's role in the Superman spot was made stronger given her secret identity as GBS TV news reporter Clara Kendall. She discovered that she wasn't actually an android, but despite this traumatizing revelation, she still nearly sacrificed herself to save all of reality. As a reward, her Earth was restored, with the caveat being that she was now truly an organic being and not an android.
Since then, the character hasn't returned in any major way. There's a chance that she could be brought back during Infinite Frontier, which is bringing back many classic elements to the DC Universe. However, it's more likely hat her heroic sacrifice and permanent death are the only things brought back into canon.