Warning: SPOILERS for Jupiter's Legacy Season 1.
Jupiter's Legacy openly questions and challenges Batman and Superman's rule of "no killing," which is embodied by the show's Superman archetype, the Utopian (Josh Duhamel). In the Netflix series, businessman Sheldon Sampson and five of his friends and relatives travel to a mysterious island in 1929. They pass a test of worthiness and are gifted with superpowers by aliens. Vowing to use their abilities to fight evil, Sheldon becomes the Utopian, and his group forms the Union of Justice superhero team. They establish a strict code of no killing and no using their powers to interfere in America's politics.
Superman and Batman's rule of not killing their enemies was forged during the Golden Age of comics in the 1940s. Originally, Batman did kill his enemies while Superman was a seeker of justice who assaulted mob bosses and domestic abusers. But as the superheroes skyrocketed in popularity with their main audience, children, Superman and Batman stopped killing their enemies and became more benign crimefighters who rounded up the bad guys and sent them to jail. Although comic books matured over the decades and into the modern-day, Superman and Batman generally held fast to their "no killing" rule, with certain exceptions depending on the story and the creative teams. But overall, the fact that the Man of Steel and the Dark Knight don't take lives became one of their defining traits in the comics and set an example for most of the other superheroes who followed them - including the characters of Jupiter's Legacy, which was originally a comic book series by Mark Millar and Frank Quitely.
The fact that the Utopian and the Union of Justice don't kill is one of the central issues of Netflix's Jupiter's Legacy. After 70 years of being a superhero, the Utopian's ideals are severely challenged by the realities of the present day, in which the younger generation of heroes the Union sired is bearing the brunt of the heightened violence and brutality the current supervillains are capable of. The Utopian is particularly distressed by the changes in society and holds even firmer to his increasingly outdated belief in The Code. Making matters worse for Sheldon is the fact that his own son, Brandon (Andrew Horton), who is the superhero Paragon and who wants to succeed his father as the Utopian someday, kills a villain called Blackstar (Tyler Mane) in order to save his father and the Union. There's no doubt that Paragon ended the fight when the other heroes couldn't, and that the other heroes would have died had Paragon not done what he did, but the Utopian can't reconcile what his son did because it is the complete opposite of the Code he swore to uphold.
The Code later backfires once again and results in a tragedy when an idealistic young heroine named Ghost Beam (Kara Royster) is murdered by the supervillain Baryon (Micah Karns). Ghost Beam's belief in the Code got her killed because she ignores her super friends' rejection of the Union and what they feel are outdated beliefs that put their lives in danger. By the end of Jupiter's Legacy, the Utopian's own faith in the Code is tested but he refuses to kill Blackstar in order to save Paragon's life. While he makes the opposite choice his son did, the Utopian comes close enough to break the Code that the experience leaves him shattered as he comes to grips with how everything he believes in may be folly after all.
Jupiter's Legacy is largely a broken mirror image of the DC Universe in the comics that puts Superman and Batman's morality to the test. The Utopian and the Union struggle with many of the same issues the Justice League in DC Comics face but with more tragic results. However, in the movies, the different versions of Superman and Batman have killed, notably in Zack Snyder's DCEU where the Man of Steel (Henry Cavill) snaps General Zod's (Michael Shannon) neck while Batman (Ben Affleck) has taken numerous lives, and the Justice League teams up to kill Steppenwolf (Ciarán Hinds). The Utopian and the old guard of the Union in Jupiter's Legacy would be appalled at the body count of the DCEU's heroes.