Nobody still knows the joker's true origin story. It is believed that he was a member of the red hood gang to get money for his pregnant wife but ended up doing wild crimes. He forgot about his pregnant wife and couldn't help them when they ended up dying in an accident.
Edward Nygma ,also known as the riddler , used to work for the GCPD and even after he went crazy he used to help the GCPD even as the Riddler. Now he knows the Batmans true identity and is considered as the most smartest and financially successful villain.
The penguin also known as Oswlad Cobblepot started of as an umbrella boy which is the reason he always carries around an umbrella. The penguin is also the only other Batman villain who is based of an animal just like batman.
Harvey's dad who was a cop used to beat him up and his dad used to determine whether Harvey would get beaten or not. Later on Harvey found out that the coin was double headed. That is the reason why he hates corrupt cops and uses a coin.
Victor Fries is trying to find a way to cure his wife after he has freezed her. He uses his freeze ray. He was originally called Mr. Zero and overall he's pretty COOL.
Dr. Pamela Lillian Isley helped her professor with stealing an egyptian artifact and he ended up poisoning her but she survived the attack and aquired the power to control herbs and plants.
Batman was not aware of Damian Wayne's existence for a considerable time. Genetically perfected and grown in an artificial womb, Damian was intended to be a formidable warrior. He is raised by Talia and the League of Assassins.
Dick Grayson was part of a circus group called the flying graysons and the circus has a history with the court of owls as they give them a new tallon every year. Dick sacrificed himself to the court to protect his family. He uses to tasers as his weapons.
Catwoman used to be a small time crook and her knickname was cat because of how stealthy she was. She is also Batman's former lover.
Bruce wayne is now Batman