Joker (Arkhamverse)

The Joker is the main antagonist in both Batman Arkham Asylum, and Batman Arkham City.

The Joker (Batman: Arkham Asylum)
The Joker was also the main villain in the videogame Batman: Arkham Asylum. He got himself locked up in the asylum, along with other so-called "super-villains" to pull off a daring scheme. He planned to build an army of super henchman by mutating his normal henchman with Titan, a venom created by a scientist of Arkham Asylum. To do this, he had to take over the entire asylum, and he was quite successful, since he managed to take control of the security system, the warden, and even over Batman. At the end of the the game he injects himself with the Titan Formula and became the Titan Joker.

The Joker's Profile States
An insanely homicidal super-villain, the Joker’s white skin, green hair, and blood-red lips belie the chaotic nature underlying his cartoonish appearance. The self-styled Clown Prince of crime has no superpowers beyond a capacity for incredible violence and a skill at creating deadly mayhem. He frequently concocts elaborate schemes to entrap his arch nemesis, Batman.

Batman Arkham City
Joker appears in Batman: Arkham City, the sequel to Batman: Arkham Asylum as the 2nd main antagonist (after Hugo Strange, the puppet to Ra's Al Ghul). It's been confirmed that the Joker has been stricken with a poison in his blood system, because of the Titan Formula. He was desperate for a cure, so he kidnapped several doctors to cure him, blackmails Mr. Freeze that if he creates a cure, Joker would give his wife Nora back, he even poisoned Batman & Gotham with the same disease. He was also planning massive breakout of Arkham City win the war between Two-Face and Penguin. In the end, He destroys his own cure and finally succumbs to the titan poisoning, taking his plans and secrets with him.

Legacy and Harley Quinn's Revenge

 * "The city is tearing itself apart over him. He planned it that way."
 * ―Batman to Commissioner Gordon over how Joker continues to destroy Gotham even in death.

After the events of Arkham City, Commissioner Gordon personally has Joker's body transported away from the massive prison, knowing that if any of his men got their hands on him, they would tear his body apart. Gordon is forced to move Joker's body to various locations over the following weeks to ensure that none of his followers break in to retrieve it, telling no one of it's location except for, eventually, Batman. As Gotham descends into chaos over the Joker's death, Batman's mind sinks lower as his depression over the loss of Talia and guilt over Joker's death begins tearing him apart on the inside.

Batman soon realizes that the Joker had made a set of contingency plans in the event of his death to ensure that Gotham is destroyed and the Dark Knight broken. As Batman investiagtes the late villain's final schemes, Harley Quinn breaks out of her imprisonment and takes control of Joker's gang in her own plans for revenge against Batman. Taking over the Steel Mill, the last location the GCPD need to evacuate to shut down Arkham City for good, Quinn takes various police officers hostage to lure Batman to a trap. Quinn's tactics prove to be successful as Batman is captured and locked in an air tight prison.

With the aid of Robin, Batman is able to escape and stop Quinn's plans, leading to her being arrested again and allowing Arkham City to officially be shut down and Batman to refocus his attention on Joker's back up plan. Investigating what is left of the Steel Mill, Batman finds a message from Joker that was made before he died and meant to be communicated to Batman in the event of his death. As Batman analyzes it at the Batcave, he locates a video message from his eternal enemy, who begins to taunt the hero and reveals one last, twisted and sick joke against Batman and all of Gotham.