Any grace notes 70something Liam Neeson brings to his aging and about to become infirm man of action in “Absolution” are pretty much overwhelmed by cliches, loose ends and overreaches in a sloppily pieced-together screenplay.

Character motivation and the hasty and incomplete “tidying up” of a messy life makes this Hans Petter Moland thriller go right off the rails and into the ravine in the slapdash third act. The director of the superb Norwegian vengeance tale “In Order of Disappearance” and its inferior Neeson remake (“Cold Pursuit”) lets his star down, as a promising start tumbles into an inept finish.

Neeson plays an unnamed collector and hunk of muscle for an underworld boss (Ron Perlman) who runs his seedy loan sharking and criminal transport enterprise out of a Boston mattress dealership.

Boss man pairs up the flip-phone-using, ’70 Chevelle SS driver with unfashionably long sideburns geezer with the boss’s Boston College grad son (Daniel Diemer) who wants to learn the family business rather than go to law school. The fake tough guy is supposed to learn from the real one, the fellow a Latin mobster (Javier Molina) nicknames” Jurassic Park”on sight. What our muscle finds himself doing is keeping the kid from messing up — fatally.

But the big man who still takes cash for sparring with up-and-coming boxers at his local gym is losing his memory. He keeps a tiny notebook to jot down simple things — the boss’s name — so that he can recall him.

His “of COURSE I remember” your name/that address/that my son died will be familiar to anyone who has dealt with someone slipping into dementia. We know the diagnosis before the corrupt Oxy peddling doc hints at it, and before the specialist confirms it.

“CTE, chronic traumatic encephalopathy.” Too many concussions — from his old man as a kid, from the ring and from the beatings he’s taken in his work and perhaps in prison — have doomed our unnamed big lug.

Just when he’s met a persistent sex worker (Yolanda Ross) newly smitten with him. Just as he’s ready to re-connect with his estranged daughter (Frankie Shaw). Ok, the diagnosis provides the impetus to the latter, but if he doesn’t tell her why he’s reaching out, will she accept his apologies?

The dialogue is mostly boiled-over “hardboiled,” such as when his grandson (Terrence Pulliam) gets “Sometimes, you have just got to walk away” advice from him.

“Mom said you were in prison. What for?”

“Not walking away.”

Neeson’s at an age where the physical demands of the brawls his characters are meant to deliver  give us glimpses of stunt men pitching in. Not a lot of 72 year-olds could knock somebody out with a single blow, although I’d still hate to be on the business end of those Irish fists.

One can wish for as graceful an exit as possible from this post “Taken” revival section of his career. But even if he’s managed his to maintain his persona better than most of his action contemporaries, Neeson really does need to take a step back and question the credibility of playing brawlers as he enters the “fall and break a hip” years that face us all.

We’ll forgive a beloved action star many a sin, but there’s no “Absolution” for swinging your fists and dodging and absorbing blows past the point of credulity. It’s not just football players and boxers who get CTE, after all.

Rating: R, graphic violence, nudity, sexual content, smoking, drug and alcohol abuse

Cast: Liam Neeson, Yolanda Ross, Frankie Shaw, Javier Molina and Ron Perlman.

Credits: Directed by Hans Petter Moland, scripted by Tony Gayton. A Samuel Goldwyn release.

Running time: 1:52