Jason was trained by Bruce, and was his ward and partner until his death at the hands of the Joker. He was resurrected by Talia al Ghul using the Lazarus Pit, and then trained by both the League of Assassins and the All-Caste.
They also interrogated Joker's henchmen who were with him during Todd's murder, in hopes to find out how the boy could have survived. Talia later restored Todd's health and memory by immersing him in a Lazarus Pit in which her father was also bathing and helped him escape the House of al Ghul.
Afterwards, Todd's body is taken by Crane's Alcatel to a hidden Lazarus Pit under Arkham Asylum where he is resurrected. When Todd awakens, he finds Crane there, who calms him and gives him a better version of the anti fear gas, all the while manipulating Todd into working with him.
After a particularly disturbing confrontation with Dr. Crews that night, Tina runs out to the docks and believes she senses her father's presence in the lake. She uses her powers to resurrect him, but accidentally resurrects Jason Voorhees and frees him from his imprisonment.
How did JASON TODD Come Back to Life? || Comic Misconceptions || NerdSync
What made Jason come back to life?
He apparenty died a number of times but was brought back to life by a lightning bolt, by a girl with telekinetic powers and by a submerged power cable. At the end of Part VIII, toxic waste in a Manhattan sewer ate away his body until nothing remained but bones.
The Joker later went too far, kidnapping Jason Todd and killing him. Ra's watched as Batman raced to the warehouse, knowing Batman won't make it. Feeling guilty, Ra's taken Jason's body and revived him as the Red Hood.
He knew Jason was killing people, and Batman couldn't live with the shame of knowing that he had unintentionally created a deadlier version of Joe Chill. This explains the tragedy of what kept Batman away but also highlights his own selfishness and irresponsibility.
In the pre-Crisis on Infinite Earths continuity, the maturing Dick Grayson grows weary of his role as Batman's young sidekick. He renames himself Nightwing, recalling his adventure in the Kryptonian city of Kandor, where he and Batman meet the local hero of the same name.
The only reason Jason isn't happy with Bruce is because he didn't avenge his death and didn't kill the Joker. He's pretty much angry at Bruce for not going against his moral code- No Killing.
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.
Batman has trained many young heroes as Robin, and while they have all been impressive on their own, DC just confirmed that one stands above the others in terms of power: Damian Wayne is the most powerful Robin.
But on one world where the Scarecrow's fear toxin has become a permanent part of the atmosphere, it is revealed that John Henry Irons, aka Steel, is immune to the effects of the fear toxin, something that not even Batman can lay claim to.
Robin did not become the Joker. The second Robin in the animated series, Tim Drake, was kidnapped by the Joker, tortured, and turned into a sidekick/pet of the Joker called Joker Junior. Batman rescued him, but he was so traumatized that he quit being Robin.
Dick Grayson became Nightwing after Batman fired him from his own mantle of Robin for getting shot by Joker. Grayson's Flamebird was Bette Kane. After The New Teen Titans, Nightwing teamed up with old friend Speedy in Action Comics #613-618 & #627-634 later collected in New Friends Old Enemies.
Traumatized, Batman takes Jason and Sheila's remains to Gotham and holds a burial with Alfred Pennyworth, Commissioner James Gordon, and Barbara Gordon. Batman blames himself for Jason's death and resolves to carry on alone, rejecting Alfred's suggestion to involve Dick Grayson, the first Robin.
Robin the Boy Wonder was actually Dick Grayson, the youngest of a family of circus aerialists, who witnessed his mother and father plunging to their deaths from a sabotaged trapeze. This murder was also observed by wealthy socialite Bruce Wayne.
Nightwing has surpassed his former teacher and shown, once and for all, that he can beat Batman in combat. Check out Batman #138, available now from DC Comics!
The Gray Son of Gotham is the title given to the greatest Talon. The Court of Owls prophesized that this would be Dick Grayson, a descendant of the Talon William Cobb. The title was briefly taken by Dick's former protégé Damian Wayne during Robin War, before Duke Thomas brought him back to his senses.
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.
After capturing Scarecrow and returning to Panessa Studios, the main floor between the cells was painted with a large, red logo of Red Hood. It was Jason's way of showing Batman that he was back and that he had forgiven him.
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 ...
Some interpretations suggest that the audience has empathy for Jason, whose motivation for killing has been cited as being driven by the immoral actions of his victims and his own rage over having drowned as a child.
The killer known as "Jason" is the reincarnation of a young boy who either died at Camp Crystal Lake due to the inattention of the camp counselors (F13-1), and whose mother originally sought vengeance for his death (F13-1), or who survived the drowning and was killed after returning to the camp as an adult (F13-2).
