Sabretooth is the title of several Marvel Comics series starring the bestial mutant Sabretooth (Victor Creed), a character primarily associated with the X-Men franchise, in which he's generally been positioned as a supervillain and arch-enemy of Wolverine.
Sabretooth was introduced in 1977 as a villain for the Iron Fist comics, but only rose to prominence after the 1986 Mutant Massacre crossover pitted him against the X-Men as one of the villainous Marauders, establishing him as an Evil Counterpart to Wolverine. Like Wolverine, Sabretooth was revealed to be Long-Lived and much older than he appeared, with the two characters' shared history dating back more than a century.
Sabretooth's state of mind is sometimes unstable, and (like his foe Wolverine) his memories have been tampered with over the decades. At some points he's been subjected to Heel–Face Brainwashing or has sincerely tried to atone for his bloody past. At others he's been forced to work alongside Marvel's superheroes as a Boxed Crook or some other type of Token Evil Teammate. Some recurring Alternate Universe versions of the character have also been portrayed as far more heroic.
However, his solo comics, set in the shared Marvel Universe, have rarely explored these aspects - he's generally been a Villain Protagonist and murderous Blood Knight rather than any kind of antihero.