I'd like a fusion of Jason Todd and the punisher.His parents were killed in a car crash when he was 5 years old and he was left to raise his 4 and 2 year old siblings,who were also killed by gang violence when he was 10.After that day he spent time trying to get gangs out of Crowrock(a new district of Gotham).During this time he became competent in street fighting and the use of firearms,as well as the tricks of the trade in all manner of lllegal activities.
He was on his own until he was Fourteen,when he was found by leatherdeamon(Batman+Daredevil) to be defending the Leatherhide(batmobile) from gangsters and was holding his own.Oridinally Jason Castle didn't want to help him,but when he saw that Leatherdaemons skills far surpassed his own,he decided to take advantage of him,deciding he would just get better than leatherdeamon and then ditch him.
Under leatherdeamons training his skills grew quickly,his mastery of street fighting and willingness to fight dirty combined with his new martial arts prowess made him a devastating H2H combatant,whilst his street smarts allowed him to outmanouver many opponents.
Everything was going fine until one day leatherdeamon found him in the act of killing a gang lord,despite the fact that he hjad always told him never to kill.After a heated Argument and a quick scuffle Bloodspiller(as jason called himself) was forced to throw an Experimental drug into leatherDeamons eyes,blinding him and earning his life long emnity.
Bloodspiller now works alone,he is one of the worlds most viscious Vigilantes prepared to do whatever it takes for punishment to be done.He is non-sanctioned by the government and is considered a criminal by most other heroes,but he doesn't care and simply sees them as posers who don't have what it takes to save the world.