Is Marvel's Death A Villain? It's Complicated
Beyond street-level characters like Spider-Man and Kingpin, as well as space-faring ones such as Star-Lord and Nova, the Marvel Universe is packed with immensely powerful beings. Characters like the planet-devouring Galactus and the multiverse-overseeing Beyonders stand head and shoulders above some of the strongest, smartest, and most magical Marvel creations. Within this elite class is none other than Death, often called Lady Death, who is the living personification of death itself and is commonly referred to as a villain. However, if you look at Death's place in the Marvel Universe, it becomes clear that this descriptor isn't quite accurate.
Death's print debut comes in the pages of "Marvel Mystery Comics" #10, with subsequent stories revealing more about her. She's the sibling and rival of Eternity, who is the living embodiment of time, and has existed in some form since the beginning of the entire universe. As the physical representation of death, her existence is necessary to maintain balance in the cosmos. For there to be life, there must be death, so it's not quite fair to call her a full-on villain. Rather, she's a neutral presence who carries a negative reputation due largely to her dark nature.
At the same time, it's impossible to ignore that she's done some incredibly villainous things in her time.
Death isn't quite a villain, but she's no hero either
Even though it's evident that Death doesn't quite fit into the villain category as she's more of a force of nature than anything else, she's certainly not a hero. Throughout her Marvel Comics tenure, she has used her incredible power and influence to do some pretty terrible things. Perhaps her most famous pet project involves the infamous Thanos, having groomed him from a young age to embrace his bitterness, fear, and hatred by committing acts of violence. Thus, by the time he reaches adulthood, he's a ruthless killer and conqueror.
Of course, Thanos is no mere fool, so how does Death manage to keep him on her side for so long? It's simple — she exploits the fact that he has grown romantic feelings for her. Every time he thinks he's finally won her affection, she pulls it away again by adding yet another caveat to the deal. This obsession is what leads Thanos to collect all of the Infinity Gems and wipe out half of all life in the universe, believing he would finally win her over. Unsurprisingly, this defining moment of the famed "Infinity Gauntlet" story doesn't get him anywhere with his beloved.
It might not be accurate to call Death a villain, but seeing as she more or less creates Thanos, one of the most formidable and destructive bad guys in Marvel Comics history, it's easy to see why she's often given that label.