Jason Todd is well known within the DC Comics universe as the second person to take on the identity of Robin, junior partner of Batman. He is also well known for his tragic and violent death.
Batman: Under the Red Hood
Batman: Under the Red Hood is a direct-to-DVD animated feature based off the comic book story of the same title. In the film's prologue, Jason - as Robin - meets his demise at the hands of the Joker. Just as he died in the comics, Jason is beaten to near death with a crowbar and then left inside a warehouse rigged to explode. Batman arrives on the scene too late; the Joker is long gone and the warehouse explodes with Jason inside.
After Jason's death, Bruce Wayne has Jason's body flown from Bosnia back to the US to be properly buried. However, Jason's body has been switched with a dummy and the real body has been taken by Ra's al Ghul, leader of the League of Assassins. While Ra's and Batman are enemies, Ra's lives by some manner of code of honour and felt that Jason's death was entirely unnecessary. Since he had hired the Joker to distract the Dynamic Duo so he could engage his plan to collapse the European economy, Ra's took responsibility for Jason's murder and decided to try and return Batman's partner to life using the Lazarus Pit. Ra's had used the Pit to extend his lifespan for over six hundred years and suspected that the Pit could also revive the dead, so he took Jason's body and immersed it within the alchemical waters. Jason did indeed return to life, but the Lazarus waters had driven him insane and he emerged from the Pit a savage animal. He escaped from the League's island stronghold and somehow made it back to America.
Five years following his ressurrection, Jason had returned to Gotham City under the guise of the violent vigilante and crime lord, the Red Hood. He had established two goals for himself: one was to take control of Gotham's underworld by killing most of the city's criminals, his idea of becoming the Batman that Bruce Wayne should have been. His second goal was to take revenge on the Joker and kill him. Throughout his endeavour he would run into Batman but did not directly oppose him, not until he abducted the Joker and tried to force Batman to kill the Clown Prince of Crime. Batman wouldn't go through with it, but Jason tried to make him decide whether to shoot the Joker or him as he would kill the Joker if Batman wouldn't. Batman managed to stop Jason by throwing a batarang into the barrel of Jason's gun as he fired. However, as a backup plan, Jason had rigged the building he was hiding in to explode. Batman saved the Joker and Jason managed to escape in the confusion.
The adult Jason Todd was portrayed by Jensen Ackles.
Jason Todd has made various cameo appearances in different DC-based cartoon series. He is referenced in Teen Titans and Batman: The Brave & The Bold, and he appears to have a memorial built in his honour inside Mount Justice in the second season of Young Justice.