He manipulated the events that led to Jason becoming Robin in the first place, just so that he could kill him. The Joker has played many cruel jokes in his time, but none were as cruel as when he manipulated the events of Jason Todd's entire life so that the boy would become a new Robin he could kill.
The Joker kept Jason in a sealed-off and abandoned wing of the asylum, tied to a chair. There, with Frank Boles covering for him, Joker tortured and brainwashed the young man. As part of a psychological plan, Joker forced Jason into believing that Batman had abandoned him, and that Batman was the true villain.
when he was kidnapped by the Joker, Drake was implanted with a microchip that encoded the Joker's DNA with nanotechnology, into him. Over time, the Joker resurfaced and periodically assumed control of Drake's body.
Robin was mentally and physically tortured by The Joker, who attempted to make him into his own image. It became too much for Robin so he began to reveal secrets about Batman to Joker. Now his skin was chalk white, and his face was permanently changed into a giant grin, Robin was now called "J.J.".
Although Kahn dispelled rumors that the process was rigged in favor of Jason's demise, O'Neil said it was possible many votes favoring Jason's death came from a single person. He recalled hearing that "a lawyer programmed his Macintosh to dial the killing number every few minutes", but had no evidence.
While he was Robin, Jason Todd saw a number of things in the fear gas, from a Pre-Crisis fear of heights to a Post-Crisis fear of failure to live up to the Robin legacy. These days, he mostly sees clowns.
Rage: Jason's most notable weakness is his rage. Batman and numerous others have told him that his rage blinds him in battle to the point of leaving physical and mental weak points open for attacks.
The Most Traumatized Robin Was Just Confirmed in One Scene - IMDb. Almost all the members of the Bat-family were shaped in some way by tragedy, especially those who wore the mantle of Robin at some point, but DC has just confirmed that Damian Wayne gets the worst trauma across the multiverse.
How did Joker torture Jason Todd? - Quora. Joker faked Jason's death & sent it to Batman, ensuring that Batman would never try and find Jason. Then, he kept him in Arkham Asylum and tortured him for almost 2 years.
In the post-Crisis DC Universe, Jason Todd was tortured and killed by The Joker in the infamous “A Death in the Family” storyline, and while Todd has been resurrected since then, it remains one of the Dark Knight's most tragic moments (and one of The Joker's cruelest).
Tim Drake as Joker Jr. Joker Jr. (or J.J. for short) is Tim Drake when he was brainwashed and tortured by The Joker in Batman Beyond : Return of The Joker.
In Joker: Last Laugh #6, Nightwing is tricked into believing that the Joker fed Tim Drake to Killer Croc. Enraged at the (supposed) death of his surrogate brother, Nightwing beats the Joker to death.
At the end of Batman #427, Jason was beaten by the Joker and left to die in an explosion.
Jason's journey to the dark side seemed like the result of multiple influences coming together. Bruce Wayne's second Robin was still suffering intense trauma following his brush with Deathstroke in Titans season 2, and Batman worsened things by abruptly relieving Jason of his sidekick duties.
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.
TLDR: Superman didn't save Jason because he was being tortured by Lex Luthor at the time in order for Luthor to create Conner Kent/Superboy. This is why he wants nothing to do with Superboy once he appears.
By 13, Jason was running around as Robin II. When he died, it said on his death certificate that he was 15 (and still undersized from his time living on the street).
The Joker shoots and paralyzes Barbara Gordon and kidnaps her father, Commissioner James Gordon. He takes Gordon to a run-down amusement park, where he cages him in the park's freak show. He forces Gordon to view blown-up photos of a wounded Barbara, lying nude on the floor after the shooting.
Soon after, spurring on by the anti-fear gas, Jason confronts Joker and dies. Death, though, isn't exactly a permanent state in comics. Jason's body is soon taken to a Lazarus Pit left by Ra's al Ghul and dunked inside. Thanks to the healing properties of the Lazarus Pit, Jason is restored to life.
Jason was the least liked as Robin (readers actually wanted him killed off), but since then, he's become immensely popular as Red Hood.
Jason Todd
Jason Todd's notoriety precedes him. This version of Robin was so unanimously disliked that when audiences were given a chance to save him or let him die, they chose to kill him. Although the margin for this decision was very small, fans despised him due to some serious character derailment.
But Jason Todd, hands down, remains the Robin that fans have hated the longest.
Jason despised Batman for not avenging his death and replacing him with Tim Drake, so he takes his fury out on the new Robin, savagely beating his successor. Jason's jealousy gets the better of him when he assaults Tim in Teen Titans Vol 3 #29.
Although Jason Todd Trains under Batman, it is Wonder Woman who is his favorite hero.
3 “Superhuman” Strength
After his little dip in the Lazarus pit, Jason comes out as a new man. Though he still has a lot of training to endure in order to get back in peak shape and grown beyond even the level that Batman had trained him, the Lazarus pit had bestowed him with some superhuman abilities.