Jason was the second Robin, who was tragically killed by the Joker. However he was brought back to life by Ra's al Ghul and the lazarus pit(explained better in my Under the Red Hood video). After being resurrected Jason becomes the brutal Red Hood, who is out for blood and goes against his mentor's no kill rule. This causes a rift in the "father and son" relationship between Batman and Jason. Jason is tempered and very angry, but supresses it with his comedic taunting of criminals, he is very mild and hates everything about criminals but still feels bad about killing them, because while he did take out a criminal he still realizes that the criminal he just killed may have a family and he just took out that father or boyfriend.