DC's Justice League Unlimited ran for three seasons from 2004-2006, operating as a direct sequel to The Justice League. The original seven founders are joined by an entourage of new heroes, including the likes of Supergirl, Question and Green Arrow. The team encounters a series of new villains, plots and adventures alike, the team dynamic switched up given the addition of more heroes.
The series provided many great storylines concerning the heroes, Lex Luthor and Cadmus, and included its usual mix of comedy and heartfelt moments. While the series boasted 39 episodes, there were 10 in particular that were rated the highest.
"For The Man Who Has Everything" (8.6)
Batman and Wonder Woman head to the Fortress of Solitude to wish Superman a "happy birthday", but come across the unexpected sight of Superman incapacitated by a strange-looking organism attached to his chest. Superman is living out a dream life in his mind, thanks to the organism, which functions off its victim's greatest desires. Superman's perfect world is gradually infiltrated as Batman and Wonder Woman fight Mongul, the villain responsible for the organism, and Batman is briefly attacked by the organism, but also has his dream-like world broken through. Mongul gets the best karma when he himself is victim to the organism, but his dream-like world doesn't sound pleasant.
"The Once And Future Thing, Part Two: Time, Warped" (8.7)
The second half of the first season finale exemplifies why it's a bad thing to mess with the time and space continuum. The villain Chronos is obsessed with making himself a God, but Batman is able to write a program that debugs Chronos' belt, erasing everything he had done, and as Batman says, ensuring Chronos never exists.
After Batman uploads the program, he and Green Lantern find themselves once more in the Watchtower cafeteria, a scene from the previous episode, with mostly everything back to normal. Green Lantern is now privy to the knowledge that he and Hawkgirl will have a son, and only he and Batman remember what happened.
"Alive!" (8.7)
Lex Luthor's hunger for power lands him in big trouble in this episode. He takes extreme measures to get what he wants, and in the process, he defeats anyone who dares to rebel against the idea of him being more powerful than all the members of the Legion combined. Even more importantly, Luthor ignores Metron's warning and unintentionally resurrects Darkseid, when he'd been seeking Brainiac. With Darkseid's promise that Earth will suffer, Luthor and the Legion of Doom turn up on the doorstep of the Metro Tower, with Luthor informing the League that there's a "little" problem; little being a major understatement.
"The Great Brain Robbery" (8.7)
A serious case of mistaken identity means ensuing hilarity when Lex Luthor and Flash accidentally switch minds--and bodies! Flash must bluff his way through as the leader of the Legion, and Luthor enjoys his newfound abilities, hoping to use Flash's powers for evil. Flash goes along with the Legion on their latest heist hoping to stop them, but Luthor clues in the Legion to the fact that Flash is an impostor and he becomes their prisoner instead. Eventually the two are switched back into their own bodies.
However, Green Lantern isn't convinced that Flash is truly Flash--until Flash begins relaying a story that quickly reassures Green Lantern that the real Flash had indeed returned.
"Flashpoint" (8.9)
Another episode containing the Cadmus story arc, the League finds themselves unintentionally at war with the Government and at odds with the people they only wish to protect when a beam from the Watchtower vaporizes a building on Earth. Several heroes, led by Flash, head to Earth to help those caught in the shock wave from the blast, but the damage has already been done. Waller convinces the President of the United States that the blast was punishment from the League for Question being kidnapped, further worsening the situation. Not only that, but the people begin to severely distrust the League, believing the blast was intentional.
"Question Authority" (9.0)
Love and conspiracy are in the air in this episode. Superman and Lois share a romantic date, but Lois voices her concerns over the people no longer trusting Superman given his actions when he was under Darkseid's control. Meanwhile, Question steals files, hoping to find a link between Lex Luthor and Project Cadmus. He initially waves off Huntress' advances, but does end up agreeing to a date.
However, Question quickly gets caught up in discovering the Justice Lords in the alternate universe and is horrified by Superman's actions, fearing the same events will happen in their world. Question confronts Superman but is unconvinced, leading him to make decisions that lead to his getting kidnapped and tortured, which Superman and Huntress free him from.
"Panic In The Sky" (9.0)
Six of the seven founders of the League turn themselves in to the authorities as a gesture to the people, who no longer trust them after the whole Cadmus disaster. Batman, however, refuses and decides to investigate as to who framed them, and it leads him to Lex Luthor. Fights break out on the Watchtower, including a notable one between Supergirl and Galatea, but nothing is as shocking as the moment when it is revealed that Brainiac was inside Lex Luthor, and he is the one behind the Cadmus catastrophe.
"Epilogue" (9.2)
This episode mainly centers around Batman: more specifically, his secret son, Terry. Terry angrily breaks into the home of Amanda Waller and demands answers, which she provides. She clears up Terry's misconceptions of Bruce's intentions and relays to him that she was the mastermind behind Terry carrying Bruce's DNA, as she believed the world would need another Batman.
The story she provides is both interesting and heartbreaking, but Terry walks away knowing he has a choice concerning whether or not he wants to be Batman, and then shares a heartfelt moment with an ailing Bruce.
"Divided We Fall" (9.3)
The League is put to the test in this episode, beginning with realizing Brainiac is within Lex Luthor's body and is now controlling him. The League faces their counterparts in the form of android replicas of the Justice Lords, forced to face their worst fears and insecurities, which each League member manages to conquer. Flash gets his shining moment in this episode, coming to everyone's rescue, but is nearly lost in the process. Luckily, his teammates come to his aid and ensure Flash is pulled out of the portal to the Speed Force, created by the fact that Flash had gone the fastest he'd ever gone. The episode ends with the League deciding to keep in better touch with the people and making changes.
"Destroyer" (9.4)
The Justice League teams up with Lex Luthor and the Legion of Doom to defeat a bigger threat: Darkseid, and his imminent invasion of Earth. While most of the League are wary of pairing up with the villains, each side honors the allegiance to fight against their common enemy around the world. Darkseid tortures Superman, wishing to force him to witness the loss of Earth before killing him, but he's deterred by Lex Luthor, and soon afterwards Luthor disappears alongside Darkseid in one blazing light. The series finale ends with most of the League believing Luthor and Darkseid aren't really dead, and with Batman giving the Legion a five-minute head start, before he and several members of the League take pursuit.