The twisted Marvel Zombies reality came into existence when a zombified version of the Sentry infected the heroes and villains of his world. Among the heroes who manage to leave this blighted planet are an undead Spider-Man, who’s eaten his Aunt May and Mary Jane. The zombified wall-crawler ends up in a different reality, one completely devoid of zombies — prior to his arrival, that is.
When he comes face to face with the Sinister Six of that world — the classic roster of Doctor Octopus, Kraven the Hunter, the Sandman, Mysterio, Electro, and the Vulture — he makes short work of most of them by straight-up eating their organs. Only the Sandman is able to survive this vicious assault, and is thoroughly shocked by the alternate webslinger’s actions. He soon encounters his world’s version of Spider-Man, whom he mistakes for the zombie. Driven by rage and self-preservation, he beats the hero to a pulp and forcefully enters his mouth, blowing him up from the inside.
Seeking to atone for murdering his loved ones (and wanting to prevent the zombie virus from reaching other worlds), the zombified Spider-Man captures the Sandman and bombards him with disease-consuming nanobots. In a climactic battle, the weaponized Sandman is unleashed upon the zombies, obliterating nearly all of the remaining undead, including zombie Spider-Man himself. The only zombie super-being spared from this fate is the Sentry, who the Watcher has trapped in a time loop.