Wolverine and Sabretooth haven't always seen eye-to-eye, as the brothers have gotten into some seriously deadly sparring matches. But, the most gruesome fight between the two mutants turned deadly, as Wolverine once used a special weapon to cut off a feral Sabretooth's head.
In Wolverine (2007) by Jeph Loeb, Simone Bianchi, and Andrea Silvestri, Wolverine seeks the Murasama Blade from Cyclops in order to kill Sabretooth for murdering Feral. The legendary sword can slow down mutants' healing factors, and as Wolverine monologues, "it's the only thing that can kill me and make sure I stay dead." Logan had given the sword to Scott as a failsafe in case he went feral and had to be put down. Reluctant to give him the sword, Emma Frost enters Wolverine's mind and is disturbed by Sabretooth's violence, recommending Cyclops "give him the damn sword." After acquiring the Murasama Blade, Wolverine goes after his brother.
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Feeling guilty for Sabretooth's actions, Wolverine encounters his brother in the woods. As Sabretooth lunges at Logan, he uses the Murasama Blade to cut his arm clean off. The feral Sabretooth tries to reattach his arm, but Wolverine explains to him that his healing factor is being slowed down. Wolverine asks Sabretooth is there's "anything left of you in there Creed?" as he offers him one last chance to live. Tears pour down Sabretooth's eyes as Wolverine slices his brother's head clean off.
While he admits to almost feeling sorry for Sabretooth, Wolverine remembers all of the women (and people) he's hurt and decides he's done the right thing by putting an end to his brother's life. If you expected Sabretooth to get a proper burial, you'd be sadly mistaken. Wolverine considers burying him, but decides it's best to let wild wolves "take it from here."
Now, this is a comic book, so Sabretooth's death wasn't permanent. He'd soon return in Hell. But, the brutal moment shows how Wolverine exhausted all of his options in dealing with Sabretooth and decided the best way to stop him was to kill him. It's a tragic scene as Wolverine's choice isn't easy. Despite all Sabretooth has done to make his and his allies' lives a living hell, he's still his brother. But Wolverine knew what he to be done, otherwise, he'd have even more blood on his hands.