SPOILER!
The held in cold whole scenery depressed at the beginning, the lonely life of Mr. Brown, who also lost his only pal by a drug gang after the death of his daughter and his wife is, well presented. Then Harry exerts merciless vigilante, triggered by an attack on him, paid by the culprits with their lives. Michael Caine plays excellently, the remaining actors are so well (after all, are 2 of Game of Thrones here). Pretty bad, I found the two investigating officers. The script is okay, even if there are some rough edges has (eg the arms dealers and the stupid policemen - or British cops so?). A little I lack the implementation of the "street battle" in the end, here you just have to assume that everything calmed down after a while. The film is pretty bloody and shot scenes come over pretty realistic (though I never let alone a hit in a human body have witnessed a real gunfight - and I do not want too!).
Nevertheless, I think the film is not bad, not least thanks to Michael Caine.