I would argue we're grafting arcs onto characters as an academic exercise, as writers are wont to do, but I don't think there's any 'there' there.
To preface: when I refer to character, I'm referring to the protagonist. And, by arc, I'm referring to the character entering the story one way, and leaving the story having fundamentally changed as a person.
In Back to the Future, Marty doesn't fundamentally change as a person. Changes occur around him, but he arrives back in 1985 as the same guy he was when he left. Which is kind of the point, really. He happens to have nicer things going on in his life when he gets back, but that's not an arc. He's happy to be back in familiar surroundings, to see his family in a better place, he's got the truck he'd been eyeing, and he's happy to see his girlfriend again. But, is he a different person internally as shown by the storytellers? My argument is, no.
We can't attribute an arc to someone just because there would be one should this happen to someone in real life. We can only go with what we're being shown, told, etc by the storyteller. Yes, you could easily imagine Marty having a fundamentally different outlook, or having changed a great deal internally from the experience he'd gone through, but if it isn't there on the page, it just isn't there.
In Mad Max: Fury Road, Furiosa rebels against Immortan Joe by absconding with the rig. The bad guys chase her. She eludes capture, then races them back to the home base, killing the chasers in the process, arrives at home base, and takes over. She leaves, she fights, she comes back. Is she fundamentally changed as a person from the experience? I think in real life most people likely would be. Is Furiosa? No, I think the mindset and internal drive that led her to act in the first place, is the same steely resolve we see written on her face as the story ends.
In No Country for Old Men, the Sheriff enters the story disillusioned, and leaves it the exact same way. If you prefer Moss as your protagonist, he might've had a chance at completing an arc if...
And, in a twisted way you could say Chigurh is the protagonist, and he definitely does not have an arc. Evil going in, evil going out.
The Big Lebowski: well... the Dude abides. He's the laziest man in Los Angeles County at the beginning, and as we see him at the bowling alley at the end, he's the same guy... the same old Dude.
Raiders of the Lost Ark: Indiana Jones exists as almost the anti-arc. Lost arc? yuk yuk Point is, he doesn't fundamentally change. Same in, same out.
In 3:10 to Yuma, Dan Evans enters the story as a moral, stand up guy trying to see a job through for the good of his family. That never changes. He never changes.
In Aliens, Ripley enters and leaves the story as the same person, only the circumstances surrounding her have changed. She went through hell in the first film, and fought the monster, and got away. The same thing happens in the second film. She fights her fear, and she slays the beast, but is she fundamentally changed as a person by the end? I don't think so.
She has warmth towards Newt and Hicks, but she was a warm person from the start. She may somewhat trust Bishop in the end, but do I think she'd enter another scenario where she's stuck in the same situation, and there's an android present, do I think that she'd be feeling different about having the android there than she did at the beginning of Aliens? No, I don't.
When it comes to seeing an arc in Ripley, I think we look for that because we know in real life if someone were to go through something like that they would most likely be fundamentally changed, but from a storytelling standpoint, I don't think it's there.
Same for Jack Reacher. You can pick up any one of those books, and read them out of order, because he's the same dude in every book. He arrives, he conquers, he leaves. Pretty much every Reacher book is a remake of 'Shane' or, if you prefer, it's more recent (though not recent at all) redux: Pale Rider. Lee Child says he's fascinated by the Knight Errant type of character, and that was his inspiration for Reacher.
In Canada, we had a similar Knight Errant type of character who gained popularity on TV. The show was called 'The Littlest Hobo', about a German Shepherd who wanders into a small town, solves everyone's problems, and leaves. Since he's a doggo, we don't watch it expecting any character arc as an audience, and that's because it isn't the point of the story. He elicits change around him, which is interesting to watch. Same for all of the stories named above. I would say all of the protagonists mentioned are all catalysts for change, while never changing themselves.
Again, I think we're prone to inventing arcs in our minds when we consume stories - sort of like your brain filling in gaps in your eyesight or hearing, or experiencing the phantom pain from a missing appendage. You could probably do this for the most plot-focused story out there if you wanted to.
And, so, I think we tend towards mistaking 'external things happening' for character growth/devolution. That's the thing I'm getting at with the above examples; 'doing stuff' is not a character arc. Having stuff or other people fundamentally change around you is not a character arc either.
