A part of the DCAU (DC Animated Universe), Justice League was an animated series which originally aired on Cartoon Network between 2001 and 2004. The show was so popular, that it would lead to the release of a rebrand/continuation series, Justice League Unlimited, in the same year after it ended. Justice League was aimed at children, although it kept a lot of its dark storylines, dealing with issues such as physical, mental, and emotional torture, death and grief, parental narcissism, and parental abuse.
The League comprised of Batman, Superman, Wonder Woman, J'onn J'onnz, Hawkgirl, and Green Lantern. In Justice League Unlimited, this core group would be widely expanded to include hundreds of superheroes working in an organized fashion to keep Earth safe.
Legends: Part II (8.8)
Green Lantern (John Stewart), J'onn J'onnz, The Flash, and Hawkgirl are accidentally transported to an alternate Earth. On this alternate Earth, they meet the Justice Guild Of America, a group of superheroes protecting the alternate Earth, just like the Justice League protects their planet. However, things do not add up for J'onn J'onnz. He knows that something is wrong. This episode is a poignant reminder of why audiences adore superheroes, as evidenced when the Justice Guild Of America courageously and selflessly give up their entire existence to save the Justice League.
Starcrossed: Part I (8.8)
The series finale of Justice League, before Justice League Unlimited would air in the same year, 'Starcrossed' begins with Hawkgirl and John Stewart's relationship still going strong. Their canonical relationship becomes very important in the series finale, when the Thanagarians, Hawkgirl's alien race, arrive on Earth. Thanagarian leader, Hro Talak, confesses that Hawkgirl was sent to spy on Earth. Batman, suspicious, spies on the Thanagarian's, finding out that they plan to take over Earth, because they are losing their home planet to an incessant war with the Gordanians. He alerts the JLA, causing the Thanagarians to attack and subdue the League.
A Better World: Part I (8.9)
On an alternate Earth, Luthor is President of the US, and has killed The Flash. Lex's power-hunger is, of course, a great fear of the JLA. Angered, Superman finally kills Luthor with his heat ray vision. This begins a new reign of the Justice League as Lords on Earth, where they impose their will on everyone to enable peace at all costs. Despite signs of dissent from Earth's population, the Justice Lords head to another Earth, Earth 1, where authoritarian peace has not been achieved.
In a surprising move, uncharacteristic of the heroes, the Justice Lords travel to Earth 1, where Flash is still alive, determined to bring order by force, as they did on their own Earth. DC Comics is well-known for dealing with the philosophical theme of unlimited power, and the dangers it brings to the subjugated. That is, what happens if superheroes turn their powers against humanity?
Hereafter: Part I (8.9)
Toyman brings his disintegrator with him to battle against the Justice League. After he aims it at Wonder Woman and Batman, Superman jumps in front of the beam and disappears without a trace. Everyone believes Superman to be dead - except Batman of course. The Justice League mourn Superman in a DC Comics' classic plot: Superman's death. Superman's death is very important in the DCU, because without Superman's specific superpowers, there cannot be peace or stability on Earth. He is Earth's ambassador and the glue keeping the JLA together. The episode ends with a shot of Superman still alive, trapped under some rubble.
Wild Cards: Part I (8.9)
Joker has set a bomb somewhere on the strip in Las Vegas, and planted cameras everywhere, He wants everyone can watch as the JLA try to find and disarm the bombs before they go off. He has also sent a group of supervillains, the Royal Flush Gang, abducted as children, and trained by the government to become a superhero fighting squad. The Justice League soon find out that there is not just one bomb, but twenty-six. An episode centered on the Joker is always a philosophical one. In the DCU, the government is always the villain, using superheroes as pawns in their games for imperialism. For the Joker, he is simply callously dehumanizing and using the Royal Flush Gang in the same way that the government did.
A Better World: Part II (9)
The Flash saves the rest of the JLA imprisoned by the Justice Lords. Soon, Justice League Batman convinces Justice Lord Batman that totalitarian peace is not the answer, and Justice Lord Batman helps them to cross back into Earth 1 to subdue the Justice Lords. The Justice League and Justice Lords fight each other, until Justice League Superman appears with Lex Luthor.
In return for a presidential pardon, Luthor uses his specially designed weapon on the Lords, draining them of their power. The episode ends with Luthor hinting that he would like to go into politics. The question remains, is it OK to kill one to save many? Will Superman have to kill Luthor on Earth 1 as occurred in alternate Earth? Is authoritarian peace better than democratic chaos?
Starcrossed: Part II (9)
The JLA are captured and imprisoned, but they manage to escape back to Earth. On Earth, the League is being hunted by the Thanagarians, so they revert back to the human aliases, so that they can find their way to Bruce Wayne's Batcave. There, Hawkgirl meets them there to tell them the truth. The Thanagarians want to build a hyperspace bypass that would allow them to enter the Gordanian's fortress on their planet, so that they can destroy the Gordanians once and for all. This would also cause everyone on Earth to perish, but this is a sacrifice the Thanagarians are willing to make.
Unbeknownst to Hawkgirl, a chip was planted on her, alerting the Thanagarians to the Justice League's location.
Wild Cards: Part II (9)
The Justice League manage to disarm all the bombs, after which the Joker reveals that the bombs were just a plot to get as many viewers glued to the screen as possible. He introduces Ace, one of the superpowered teenagers hidden by the US government, because her powers are too strong. Ace's gaze drives people crazy, completely destroying anyone's mind if they look into her eyes for a few minutes. When Batman attacks Joker in the TV studio, he pulls out the band that the US government used to disable her mind. Ace is furious when she sees the band, reliving her traumatic childhood. Angry at the Joker for exploiting her pain too, she turns her gaze onto Joker alone, freeing the viewers watching her. Earth is saved once more.
Hereafter: Part II (9.1)
Superman has been transported 30,000 years into the future. There, the last survivor on Earth is Vandal Savage. Without Superman there to stop him, Vandal built a superweapon and killed the Justice League to become ruler of Earth. Unfortunately, his superweapon also caused everyone on Earth died. Savage has time to reflect on himself, and comes to believe that his quest for power was meaningless.
DC Comics has always explored the psychological reasons for villainy, the Joker being an obvious example. This time, Vandal reveals that he was driven to villainy, because he could not face his existential fear of self, of life, and of death. In the end, he deduces that life is meaningless without others to share it with.
Starcrossed: Part III (9.3)
Hawkgirl is also arrested and imprisoned upon her return to the Thanagarians. Her lover, Talak, is enraged to find out that she sides with humans, and that she is in love with John Stewart. Batman guides the watchtower to crash unto Earth, directly on the hyperspace generator so as to destroy it. He knows that this would kill him, but is willing to make the sacrifice. The rest of the JLA fight the Thanagarians successfully, with John taking out Talak.
The Thanagarians concede defeat, and Superman saves Batman just before the watchtower crashes into the generator. In the final scenes of the series, the JLA vote on whether to allow Hawkgirl to remain a member. Despite their aura of strength, even the League cannot boast impenetrable or unlimited power.