"From a man who knows, THAT'S CRAZY TALK!"
Joker to Weeper when the latter says he's not evil enough to be a supervillain
Joker is a villain in the DC Universe and the archenemy of Batman.
The Clown Prince of Crime
Origin
No one is certain how the Joker came to be: All that's known is that he fell into a vat of chemicals, which bleached his skin to a chalk white hue, stained his lips bright red, and dyed his hair a sickly shade of green. Some say he was a career criminal named the Red Hood who planned to steal money from the Ace Chemical Plant, and dove into the chemicals to escape ; Others say he was a mob boss and accidently fell into the chemicals while fighting Batman; Some say he was a hitman who was accidently disfigured by Batman in retaliation for injuring a girlfriend of his alter ego, Bruce Wayne, and was later dumped into the chemicals by his employers. Whatever the case, the Joker is Batman's most unpredictable adversary, always thinking up a new, flamboyant crime, leaving a pile of fresh, disfigured corpses in his wake.
History
Joker tortured Batman over the years by committing crimes the only his twisted mind could imagine but Joker teamed up with Batman when Owlman dressed as Batman started committing crimes which stole Joker's limelight. Although Joker did betray Batman in the end he admitted that he enjoyed working with Batman and that maybe if he wasn't a homicidal maniac and Batman wasn't a do gooder they could have been friends. Joker then precedes to tell Batman that next time he'll have the trump card and gives his trademark laugh before being loaded into the police wagon and taken back to Arkham Asylum.
Even after the incident Joker would continue to be a constant adversary of the Dark Knight. He appears in Season 2 episode 18 'Emperor Joker' where from an accident while fighting Batman he obtains Bat mite's powers he then uses them to create his own Joker mite and kill and revive Batman only to kill him again and repeats the process over and over again until Batman tricks Joker into trying to take away his sanity where he sees a world where Batman doesn't exist and he's perfectly sane, Batman releases him after he says he'll give up his powers , he's then left drooling while Harley Quinn comforts him.
Powers
Joker has no superpowers, but is an expert of hand to hand combat, and a master marksman. He also carries razor sharp playing cards, has a deadly hand buzzer on his hand, trick streamers that wrap up the target up his sleeves, his jacket can turn into his version of Batman's jet pack and even a bazooka hidden in his pocket and has been seen with machine guns and pistols one of which fires a bullet with two boxing gloves that burst out before impact
Weapons
Joker employs an arsenal of joke and comedy weapons, and his own laughing gas, which causes his victims to literally laugh themselves to death, and leaving them with the Joker's hideous smile and appearance on their face. He even carries the same ridiculusly long barreled revolver (although the make and model is debatable) he used in the 1989 Tim Burton movie.