The Joker is an infamously extreme and formidable psychopathic crime lord from Gotham City, being at the very top of the city's criminal underworld, greatly feared by all other crime bosses and criminals, including his long time rival Roman Sionis. Though he is devoid of empathy or pity for anybody taking part in his wicked schemes either by intimidation or fraud, the Joker used to adore his on-and-off girlfriend and partner-in-crime Harley Quinn, doing his utmost to rescue her from Task Force X and the clutches of Amanda Waller, with eventual success. For unknown reasons, he later broke up with Harley, leaving her on her own and a target of many of his enemies. The Joker is also the longtime archenemy of Batman, whom he considers to be his own favorite "joke" and the murderer of the latter's protege, Robin, alongside Harley Quinn.