Of all the steadily slower-moving action pictures Liam Neeson has stumbled into the sunset with in the latter stages of his action hero career, “The Marksman” stands out as the stupidest.

A tedious pastiche of other “tough guy on the run with a kid” variations, it’s built on a somewhat gutless, gun-happy turn by Neeson, a fine actor playing a character who has less of a redemption story arc than a villain who has few lines and lots of closeups, a child co-star who has no chops, obvious plot turns and a laugh-out-loud dumb finale.

Think “Witness” rendered “witless.”

Neeson plays Rancher Jim, a recently-widowed loner with “underweight” (no money to feed them) cattle and a drinking problem. He’s in foreclosure, and he lives along the Arizona border with Mexico.

He avoids cell phones, but keeps a walkie-talkie in his truck, tuned to a frequency where he can summon Border Patrol whenever he stumbles across a cluster if “IAs” (“illegal aliens”) crossing his property, often in bad shape.

Jim’s got a Marine Corps tattoo on one arm and an eye that still fits his medium-sized-magazine rifle’s scope like a glove. We see him take out a coyote. That shows his accuracy, and the fact that they coyote was finishing off a dog it killed maintains our hero’s righteousness.

That’s a tone-setter, and it’s important, considering what follows.

South of the border, a mother (Teresa Ruiz) and her boy (Jacob Perez) get a warning that their family’s got fresh cartel troubles and it’s time to flee. Their paths will cross Jim’s in a flash. And as they slip through the border fence, the armed black Suburban gang led by mob lieutenant Mauricio (Juan Pablo Raba) rolls up behind them on the Mexican side just as Jim calls in more “IAs” on the walkie.

Could this be a “Mexican Standoff?”

Jim barks “Speak English” at them, and then gives them his best taste of tough guy.

“Sorry, Pancho. These illegals are mine.”

This is the guy Jim needs to be for this movie to work. This is the guy good guy Liam waters down and refuses to give any edge. He’s set up as an embittered, racist immigrant hater. And Neeson doesn’t dare play him that way.

When the mother is shot and begs him to get her boy to relatives in Chicago, we remember his earlier, callous dismissal — “It’s a cruel world.” His reluctance to take her request seriously, desire to follow the rules and protocols, and then abandon that on a quest for humanizing redemption only works and makes sense if there’s a big dose of Joe Arpaio in him.

Without that, his coldheartedness loses its sting. Leaving the kid with a Border Patrol team led by his stepdaughter (Katheryn Winnick) is all he’ll do. Instead, a MacGuffin is introduced that changes his credo, and seeing the bad guys again (and not reporting them) gives him a mission.

The cross-country chase is the usual collection of “Eat, what’s the matter with you? No hablo ingles?” (He just saw his mother murdered.) cliches and tech-savvy mob tracking and pursuing.

There’s a kid and a /Jim’s dog on the journey, and you know what means. Got to hit a “good guy” gun store to buy off-the-books firearms. Got to teach the expressionless child in his charge how to use a pistol.

And as the gangsters murder and bribe Border Patrol guards and sheriff’s deputies cross country, we wonder how long before we get to the biggest “Witness” borrowing of all.

“The Marksman” is set up like a lot of the movies Mel Gibson is making of late — violent, self-righteous and unapologetic. Jim is literally wrapped in the flag in one scene.

But the slow, stumbling progress of the picture matches Neeson’s uncertain footing in the character. He doesn’t want to make him hateful, can’t even bear to let him be unlikable. He stops at a church. He figures out the kid loves Gummy Bears (product placement in a lot of movies these days).

But a hero’s journey isn’t epic unless there’s a broad character arc, a big change in who he is by the story’s end. Redeem a believer? No big deal. Convert Mary Magdalene and you’ve done something.

This kid is bland, and all these faraway-eyes closeups of Raba (TV’s “Wild District,” “Shot Caller”) make us wonder what the script has in store for our standard-issue murderous psycho. Oh, that’s a doozy.

All these waypoints where the movie gives us an excuse to check out or just shake our heads make “The Marksman” a thriller that misses the mark, and not by a little.

MPA Rating: PG-13 for violence, some bloody images and brief strong language

Cast: Liam Neeson, Jacob Perez, Katheryn Winnick and Juan Pablo Raba.

Credits: Directed by Robert Lorenz, script by Chris Charles, Danny Kravitz and Robert Lorenz. An Open Road release.

Running time: 1:48