MUTT

When Grace Misty Firewinter was little, around six, her mother died and her father became a very wealthy scientist because he came up with a biological mutant chemical. When she was eleven, she was exploring her father's lab and spilled some of the chemical and inhaled it. It made her into a genetically modified mutant. She is able to access 25% of her brain, element control and Grace has Combat Enhancement. She told her father but like always, he didn't care.
When she was 12 he sent her off to an elite boarding school. Grace was trained as an assassin by a man named Mr. E. He trained her in archery, knife skills, and acrobatics. She was supposed to go into the MI-five in London but she dropped out of school. Grace's father was furious but he had to allow her to stay. He ignored her until she was 14. One day while visiting him at his labs they got into an argument over a pencil. She ran away upset and the next thing you knew her father was on the ground, bleeding. Someone killed him. But they weren't aiming for him. They wanted to kill Grace.
She went on the run. She withdrew all the money he left her and backpacked around New York for a couple months until she bought an apartment. When Grace was 15, credited with over 32 kills, she was targeted at the apartment so she took her back packing to the sewers and now lives a double live as Grace Firewinter and the superhero Raphael.