Death Wish 3 (1985) on Netflix

Paul Kersey returns to New York to visit his friend Charley, who lives in one of the worst parts of New York City. But when Paul arrives at Charley's apartment, he finds Charley dying after a vicious beating by a gang led by Manny Fraker, and the police enter the apartment and find Paul standing over Charley's body. Paul is arrested for the murder, but police chief Richard S. Shriker is like Paul with a badge -- he's a big fan of Paul. Shriker offers a deal: Paul can kill all the punks he wants to kill, if he keeps the cops informed about the death count. Shriker releases Paul to go after Fraker. Paul moves into Charley's apartment in a decaying building in the middle of a bombed out gang war zone. The building is populated by a group of elderly tenants who are absolutely terrified by Fraker and his gang. Among the tenants are Charley's friend Bennett, an old watch repairman who keeps a couple of machine guns in his closet. There is also an elderly Jewish couple who live on the first floor. The neighborhood is ruled by Fraker, who wears a reverse Mohawk: He keeps his hair on the sides, but shaves down the middle, to make room for a gang symbol in war paint. Paul buys a .475 Wildey Magnum with exploding big-game cartridges, spends an afternoon planting explosive charges in the bullets, and loads up for war against Fraker.