This movie is all about Logan’s guilt. He carries it with him everywhere. Remember his dialogue with Laura about their dreams:

Laura: “People hurt me (in my dreams)."
Logan: “Mine are different. I hurt people.”
Laura: “I hurt people too. Bad people.”
Logan: “All the same.”

Think of all the dialogue from Shane, about how killing is a brand that stays on you, one you can never wash off, something that changes you forever. Think about how many times Logan insists he *isn’t* a hero, that the comics were fake, that he’s not the good man people think he is. He’s haunted by it. Shit, the survivor’s guilt alone from being the only X-Man to walk away when Charles killed the rest of the team (the “Westchester incident” you hear about on the radio as they’re leaving Vegas).

Logan’s greatest nemesis isn’t some arch villain in a gaudy leotard. It’s his past—it’s everything he remembers, and everything he wants to forget. That’s why X-24 works perfectly, imo. He’s the pure distillation of Logan’s regret—the killer working off pure rage, a weapon programmed by men in lab coats and turned loose to murder without thought or hesitation. The memory of what he was haunts him still, and then suddenly it takes physical form and stares him in the face. The first time they see each other, X-24 sizes him up and just walks right past him. It’s like he’s assessing a threat, and then realizing “This man is no threat to me—he *is* me. Just another weapon, another killer.”

To introduce a “shocking twist villain from his past!” in the form of Sabretooth would just have nudged this movie that much closer to the usual X-Men films, with their melodrama and cartoon villainy. Logan was such a terrific film for bypassing all that shit and just telling a story of a haunted man still learning to live with it (which is, not coincidentally, one of the last pieces of advice he gives to Laura—"find a way to live with it").