Avengement

 A prisoner (Scott Adkins) is taken from jail, under heavy police custody, to the hospital where his mother lies dying. They arrive too late.
 As the title card takes up the whole screen, we hear the sounds of a scuffle and muffled groans... and cut to Adkins leaving an elevator full of fallen policemen and quietly escaping the hospital. To get his Avengement, you'd presume.

 And you'd presume right. An unspecified amount of time later he breaks into a pub full of gangster types, pulls out a shotgun, and holds everyone hostage. As he makes his demands and spars (verbally and physically) with assorted hoodlums, the movie flashes back to fill in the blanks of Cain's (groan) backstory and motivations.

 Avengement is the third and latest collaboration between Adkins, director Jesse V. Johnson, and writer Stu Smalls. This is a lot grittier than Accident Man and quite a bit more dour than The Debt Collectors. Its story is both simple and razor-focused on Cain's quest for revenge, its time-jumping organically incorporated into the dialog: segues followed as Cain recounts and remembers the chain of events that ended up with him going after his brother's blood.

 Everything gets explained away; Obviously, important things like who the hell this Cain character is anyhow, what he's up to, and why... but even minor details get filled in, ranging from where he got the shotgun to (in a pretty funny touch) an origin story for each one of his scars.

 And of course those asides include a ton of fights. Brawls, more like, don't expect any wall-running or acrobatics; While very well choreographed and shot, they're kept simple and (mostly) realistic. There's an appropriate focus on brutality and on the bloody aftermath of the attacks, a lot of wince-inducement to go with all the excitement.
 The low-and-dirty tone extends to the locations (which show London at its dingiest even in the obligatory nightclub action scene), the plot points (which include some really loathsome petty organized crime activities), and the acting, which has everyone at peak nasty bloke. I'm not an expert on British accents, but everyone seems to be having a lot of fun putting on their cockney.
 I had some trouble buying Adkins as a dangerous badass, but that's mostly on me for watching too many of his podcasts and interviews (the guy is as pleasant and good-natured as they come.) He's got a lot of makeup (scars) on him here, and does pretty well by the material despite my minor misgivings.

 It's not without its grace notes. Cain's relationship with his mum (Jane Thorne) is touching, and there's a redemptive arc which feels a bit forced but kind of welcome after being submerged under all this scum for more than an hour. There are also a few pretty funny lines here and there and a minor role for Louis Mandylor.
 I sometimes felt like it was trying a little too hard, but all in all it's a great little bit of genre meanness: lean, punchy, and badass. Cain describes himself at one point as a hardened, rusty nail, a great line that also fits the movie.