Joker's Daughter AKA Duela Dent is a villainess in the DC Universe and an enemy towards Batman.
Duela Dent was the daughter of an affluent Gotham couple. At a young age, Duela has demonstrated some disturbing tendencies, which were exacerbated after her father secretly killed her pet pug dog. She became anorexic and began to self-mutilate herself. After cutting her face, Duela received plastic surgery, but during the procedure she twitched too much under the surgeon's scalpel, resulting in her face getting more damaged. Eventually, Duela, along with her new pet named Cat, ran away from home and into the Gotham City's Nethers, which was an underground cave system populated by escapees from Arkham Asylum. At some point following the Joker's recent return, Duela found his face/mask, and donned it, becoming the Joker's Daughter.