Joker's blood was killing him because of a mutated form of Creutzfeldt–Jakob disease (CJD), dubbed the "Joker Infection," a fatal, prion-based illness resulting from his exposure to the Titan formula, a super-steroid derived from Bane's venom; the Titan chemicals caused proteins in his blood and fluids to misfold, leading to a rapid, incurable degeneration that ultimately caused his death in Batman: Arkham City.
The hallucination of Joker revealed he had pumped four pints of his blood into Batman which could explain why the cure was ineffective. It is unclear whether or not Joker knew the long-term effects of his blood.
Unfortunately, it was later revealed that Henry was never immune to Joker's blood and was pretending to be so as part of his own machinations.
In addition, we can assume that Arthur suffers from pseudobulbar affect, or emotional incontinence, which is a disorder of regulation of emotional expression, caused by neurological disease or injury affecting the brain.
In universe answer: Batman is opposed to crippling, torturing, killing, and using guns. He feels that crippling and torturing are just as sadistic and evil as murder, seeing as they make the victim want to die.
The story implies that the Joker is immortal—having existed for centuries in Gotham as a cause of tragedy after exposure to a substance the Joker terms "dionesium"—and is able to regenerate from mortal injuries. "Endgame" restores the Joker's face, and also reveals that he knows Batman's secret identity.
The Joker broke his own neck. The narration in the comic goes "With a devil's strength... he twists... and twists what's left of his spine goes...." And then it is broken.
Everyone knows Harley Quinn as the Jokers' girl, but how did she become Harley Quinn? Personality Disorder, specifically, Histrionic Personality Disorder plays a key part in Harley Quinn's life.
JOKER'S LAUGHING DISEASE...
Arthur Fleck clearly had a diagnosis of pseudobulbar affect—uncontrollable episodes of crying and laughing, made worse by any emotional content. In the US alone, 1.5-2 million people suffer from this condition. During his laughter, there was always a deep sorrow and agony underneath.
Emperor Joker was a form The Joker took after tricking Mister Mxyzptlk into donating 99.99% of his reality powers to him. As a direct result, he became near-omnipotent and created a hellish world in his own image.
Batman and Freeze engaged in a fight, and Batman was able to defeat him and opened the safe, but Harley Quinn was able to break into the safe and stole the other vial. Harley Quinn was ambushed by Talia al Ghul, who stole back the cure for Batman.
There's no single consensus, but Batman: Arkham Origins and Batman: Arkham Knight are frequently cited as the weakest, often due to Origins' feeling like DLC with repetitive Riddler challenges and Knight's overreliance on the Batmobile. However, some consider the original Arkham Asylum the weakest due to aging mechanics and a simpler story, while others find Knight's PC launch and story issues make it the worst despite its polished gameplay.
He was a downtrodden man who had been pushed to his breaking point by the cruelty and uncaring of the world. Therefore, his transformation into the Joker represented the dark impulses we all have, and the potential for evil and malevolence that can result from a person pushed to their limit.
Since the Joker's apparent death in the bat cave, his body happened upon a pool of the substance dionesium which healed wounds and revived the dead. Within the pit, Joker grew a new face which he would go on to use during his endgame.
In Joker, Thomas Wayne (Batman's father) and Penny Fleck (Joker's mother) are key characters. Penny claims that Thomas is actually Arthur's father.
The bathroom dance in Joker wasn't in the script, but it ended up defining the movie. An improvised moment became the axis around which Arthur Fleck's transformation spun, reshaping both the narrative and the cultural afterlife of the film.
If diagnosis is applied piecemeal, and the patient's total picture is not taken into consideration, four or five separate psychiatric diagnoses could be listed rather than a single "borderline personality disorder" diagnosis. This happens frequently.
Gotham's Descent into Anarchy
Arthur Fleck's transformation into the Joker doesn't happen in a vacuum. It's intrinsically linked to the state of Gotham City itself. This isn't the gleaming metropolis we sometimes see; this is a rotting, corrupt, and uncaring city that mirrors Arthur's internal decay.
Harley Quinn is bisexual and has been in a relationship with The Joker, and, more recently, in a non-monogamous relationship with Poison Ivy. Other characters have been portrayed as bisexual in Batman media adaptations. Gotham's Barbara Kean and Tabitha Galavan are also confirmed to be bisexual.
Following her transition to the main DC canon in 1999, Harley Quinn was established as having immunity to toxins and enhanced strength, agility, durability, and reflexes, which she received after having been injected with a serum concocted by Poison Ivy.
Despite both characters being hyped up as super crazy, neither is usually portrayed as all that crazy. They're both pretty aware of the world around them and their own actions. That being said The Joker is usually calculating and willfully malevolent, where Harley acts out of a genuinely twisted understanding of love.
Suddenly, he pulled out a knife. Bruce tackled him from behind and Jerome dropped the knife as he made a quip saying "What hero tackles someone from behind?" Bruce brutally beat him down to the ground and jumped on top of him. He continued to punch Jerome in the face until his face literally started to come off.