Amalgamation of Harley Quinn and Deadpool.
Harleen Wilson was once a worker at the program that created Hyena and Nightclaw. When Hyena was recaptured, she was in charge of his “re-education” but soon became smitten with him. After helping him escape, Hyena revealed that he used her and tried to kill her because she had outlived her use, leaving her with a scarred face and mind.
Hyena escaped and left her at the program where she was punished for helping him escape by becoming their newest test subject. After a year of horrific experiments, she developed regenerative powers, as well as enhanced strength and agility. Scars she got before getting her regeneration powers remained though, leaving her face and body with the scars left by the Hyena.
She later escaped and took up a job as a mercenary. She’s also known as “the merc with the laugh”.