Tapped Out (2014) on Netflix

Plot summary

At twelve, Michael Shaw is a karate prodigy when his parents are killed in a carjacking; hiding in the back seat, he sees the tattoo on the killer's neck. Seven years later he is a troubled teenager living with his grandfather, and after trouble at a party he is ordered to serve community service at a struggling karate school run by Reggie Munroe, a friend of his father. There he picks up the sport he gave up. Reggie's niece Jen brings him to a local MMA fight, where he recognizes one of the fighters as the man who murdered his parents. The police cannot act without evidence and promoter Lou bars him from the circuit, so Michael accepts Reggie's offer to train him, keeping his reason to himself.