The Joker may have killed Jason Todd, but some of the worst damage done to Red Hood’s psyche came as a result of his own father figure, Batman.
The two most influential people in Red Hood Jason Todd‘s life are none other than Batman and The Joker. One raised Jason like a son as the second Robin, the other murdered him. Quite the contrast, but in Red Hood’s mind, Batman did just as much damage to his psyche as Joker did, if not more, and it largely boils down to his hair color.
When Jason Todd was originally introduced in DC’s pre-Crisis continuity, he is shown to have naturally blond hair. Upon adopting the Robin mantle, he dyes his hair black (at Batman’s request) to ensure that villains wouldn’t know that he wasn’t the first Robin aka Dick Grayson. After Grayson’s parents were murdered, Batman, understandably, felt a profound connection to Grayson (considering how his parents were also murdered in front of him) and he evolved into a father figure of sorts for his raven-haired ally.
Despite following DC’s post-Crisis continuity, where Jason’s hair color was always naturally black, Grant Morrison and Philip Tan somewhat adopt that pre-Crisis continuity with regard to Jason’s hair in Batman & Robin #5. Granted, Jason Todd’s original hair in this comic series is shown to be naturally red here instead of blond, but that’s beside the point. At this point in his life, Jason Todd keeps his natural red hair, but that same hair is starting to fall out and has adopted a white streak. He admits to his sidekick, Sasha, that he’s losing his hair not just because of the after-effects of the Lazarus Pit, but also because Batman made him dye his hair black so that he would look like Dick Grayson.
More than likely, it was for the same reason why pre-Crisis Jason did it to himself, to make criminals believe they were still battling the original Robin. Whether he intended to or not, Bruce worked hard to keep Jason in Dick’s shadow. This is ironic because a few issues of Batman & Robin earlier, Alfred tells Dick that to be a successful Batman, Dick must make the role his own rather than try to imitate the predecessor. Bruce never offered Jason that same grace as Robin. It’s no wonder why Jason carries so much resentment towards Bruce, even more than he carries for Joker. Of course, Jason has always been bitter towards Joker for killing him and even more so that he’s still alive, but he’s never harped on Joker’s crimes as often or as venomously as he does Batman for his shortcomings as a father figure. In fact, because of Jason’s resentment fo Bruce, his entire “Revenge of the Red Hood” story arc in Morrison’s Batman & Robin is fueled by Red Hood’s desire to be a better crime fighter than Batman ever was.
Both Batman and Joker played hefty roles in transforming Jason Todd into Red Hood, but while Joker’s cruelty is expected out of a villain, Batman’s is what truly hit Jason to his core.