Batman's moral code isn't the only flawed aspect of this, Joker has been spared the death penalty in the past due to being insane and as such its seen as unjustified to execute him.
In his mind, Batman pictures an ordinary man who was so broken by the world that he became a monster. Far from being happy about it though, Batman recognizes that such an existence must be utter torture. Whoever the Joker was before, he doesn't want the life he's leading now.
Why does Batman stop people from killing the Joker?
Joker Would Be the Start, Not the End
Batman does everything he can to save lives and prevent his own traumatic origin repeating, and whenever he's granted more power, he still pushes himself as far as he can go. Because of this, once murder was on the table, there would be no way to remove it.
Batman Saw the Joker's Death as a Personal Failure
He further learns that there are some worlds where the Joker is no more. But Halliday's corruption has either resurrected them or made the existing ones go haywire.
In Batman Begins, he comments that he avoids killing to avoid become like the criminals he faces, believing that doing so will make him no better than his enemies. In The Dark Knight, Batman comments that he "only [has] one rule", likely referring to this.
The Joker has had various possible origin stories during his decades of appearances. The most common story involves his falling into a tank of chemical waste that bleaches his skin white and turns his hair green and lips bright red; the resulting disfigurement drives him insane.
Seeing Jason as he was back then though, would have overwhelmed Batman with guilt and shame, perhaps even convincing him to retire as a hero entirely. This in turn showcases that Batman prioritized his own needs over Jason's. He knew that he could have helped his son, but he chose not to because it was easier.
Batman is convinced that if he kills the Joker he'll sink to his level and become something like him. Joker echoes this sentiment frequently while badgering Batman about their many similarities. If Batman really believed he was as limitless as he says he is, he wouldn't be so scared of losing himself so easily.
The following article contains spoilers from Batman:The Knight #6, on sale now. Batman doesn't use guns. That fact has been one of the core principles of his character almost since the moment he debuted. The reason is obvious: his parents were killed with a gun, ergo he despises them and anyone who uses them.
This allowed the book to explore and introduce new villains, though few proved as compelling and entertaining as Joker. Thus, the primary reason Batman doesn't kill Joker is simple: he's a sales boom.
Rigging it to explode, Joker planned to test Batman on whether he'd save Harvey or Rachel. While in custody, Joker gave the address as the place where Harvey Dent was being kept. Believing the clown to have told them the truth, Gordon mobilized the GCPD to get to the location before it exploded.
The classic story saw Batman fail to save Jason from the Joker, who beat Robin within an inch of his life with a crowbar, before finally killing him when he blew up the warehouse where Jason lay incapacitated inside.
Blaming himself for Jason's death, a guilt-ridden Batman resolved to carry on alone. He even turned down Alfred's suggestion to involve Dick Grayson, his original partner.
What did Batman do to Joker after he killed Jason?
As a result, the Joker was reprimanded to Arkham Asylum, which resulted in the Joker meeting Dr. Harleen Quinzell, and ultimately escaping with Quinzell as his future partner in crime and "Queen" Harley Quinn. Though brought back to life, Todd was permanently scarred by being revived after such a brutal death.
In reality though, the Joker has him locked up in an abandoned wing of Arkham Asylum and proceeds to further torture him for about a year - warping his mind and making him believe that Batman just simply didn't care about him, abandoned him, and quickly replaced him with Tim Drake (Todd doesn't know that Batman thinks ...
It was Jason's way of showing Batman that he was back and that he had forgiven him. A much smaller version of this symbol could also be seen on the wall (near the door) on the outside of the storage depot where Batman surrendered to Scarecrow.
What if Jason Todd had never died? Batman wouldn't have become as dark and depressed after and Tim probably wouldn't have tried to become Robin immediately, although he probably would have figured out Bruce's identity. Jason, however, did have an anger problem which possibly led to the death of Felipe Garzonas.
The psychopathology Arthur exhibits is unclear, preventing diagnosis of psychotic disorder or schizophrenia; the unusual combination of symptoms suggests a complex mix of features of certain personality traits, namely psychopathy and narcissism (he meets DSM-5 criteria for narcissistic personality disorder).
Later, Arthur goes to Arkham State Hospital and steals his mother's records, and finds out that he was in fact adopted, and that Thomas Wayne is not his father and that Penny is not his true mother.
Created by Bill Finger and Bob Kane, the character first appeared in Detective Comics #33 (November 1939). Batman: Three Jokers #1 (August 2020). In Batman's origin story, Joe Chill is the mugger who murders young Bruce Wayne's parents, Dr. Thomas Wayne and Martha Wayne.
Bruce tells Diana that he regrets failing Superman and asks for her help in forming a team of metahumans to protect Earth in Superman's absence. As they leave, the dirt atop Clark's coffin levitates.
However, Batman's most hated villain is surprisingly one of his least famous - a figure who has appeared in multiple movies, only to be quickly forgotten by fans. In Kevin Smith and Walt Flanagan's Batman: Cacophony #1, Batman faces off against Victor Zsasz (aka Mister Zsasz).
The first villain Batman ever faced was a man named Stryker. Despite that legacy, there's a good reason you don't see him around. In 1939's Detective Comics #27, Batman punched him over a railing into a vat of acid. His immediate feelings on the matter: “A fitting end for his kind.”
