Ra's Al Ghul

Ra's Al Ghul is the leader of the League of Shadows and an international eco-terrorist who has lived 700 years due to the Lazarus Pit, which can cure any ailment and even bring a person back to life. Ra's has a very mysterious past and doesn't mention it a lot. However, it is widely believed that Ra's was born around 600-700 years ago in Arabia, and was a solider for the Sultan. He was heavily respected and was a great warrior.

However one day, he was fighting in the Sultan's army when he was killed in action. His body was salvaged by a religious madman and was put into a Lazarus Pit. Ra's was resurrected and learned the locations of the other Lazarus Pits, and obtained information that most of the pits were located in Gotham City. After 300 years, Ra's slowly built the League of Shadows and moved to Gotham, becoming a terrorist.

Ra's eventually learned of Gotham's protector, Batman, and decided to make him the heir to the throne of the League of Shadows. But Batman didn't want to be the leader of a terrorist group, and so Ra's became a threat that Batman and all of Gotham would never truly be rid of. Ra's has died many times in his immortal life, however due to him having access to the Lazarus Pit, which resurrects him.

Ra's terrorist group, the League of Shadows, is focused on restoring balance to the world usually by killing a whole lot of people. Ra's is a mass murdering monster and an evil dictator, however he does have a great deal of respect for Batman, always referring to him as "detective".