Sin-Eater is a name given to several characters appearing in American comic books published by Marvel Comics. The character usually appears in comics featuring Spider-Man and Ghost Rider.

The character was introduced in Peter Parker, the Spectacular Spider-Man #107 (October 1985).

Stanley "Stan" Carter was born in Fort Meade, Maryland. He was an agent of S.H.I.E.L.D. working in research and development. He was injected with experimental drugs to increase strength and endurance, but when the program was designated too dangerous it was discontinued. Carter became violent and resigned from S.H.I.E.L.D., eventually becoming a detective with the New York City Police Department. After his partner was killed by several young criminals, Carter became obsessed with killing anyone who "sinned" by abusing authority.

As Sin-Eater, his first victim was Captain Jean DeWolff (in "The Death of Jean DeWolff" story arc). As a detective, he is assigned to find the killer, and works closely with Spider-Man. His next victim is Judge Horace Rosenthal, a friend of Matt Murdock. During his escape after killing Rosenthal, he is attacked by Spider-Man and kills a bystander during the battle. When Spider-Man and Daredevil discover that Sin-Eater's next victim will be Betty Brant, they rush to save Betty. Spider-Man goes into a fierce rage and nearly beats Sin-Eater to death. As he is being transferred to Ryker's Island, a vengeful mob including DeWolff's father try to kill him, but Daredevil and Spider-Man intervene.

Carter is put in psychological and medical care, but is crippled by the beating Spider-Man inflicted. S.H.I.E.L.D. purges all the drugs from his system, but he still has visions of his Sin-Eater persona. After Carter is released, he returns the favor Spider-Man did him by rescuing the latter from an angry mob, and begins writing a memoir of his career as the Sin-Eater. However, he has trouble readjusting to society. Finally he snaps, taking an empty shotgun and goading police officers into opening fire on him. Carter is killed, though finally freed from the Sin-Eater persona's control.

Long after his death, Sin-Eater is resurrected as part of Kindred's plot against Spider-Man. While in their safehouse, the Inner Demons are attacked by the revived Sin-Eater. Overdrive escapes and is pursued by Sin-Eater for three days. Overdrive comes to Spider-Man and begs for him to protect him, but is ambushed and killed by Sin-Eater. After being brought to a morgue, Overdrive mysteriously comes back to life with no injuries.

When the Lethal Legion (consisting of Count Nefaria, Grey Gargoyle, Living Laser, and Whirlwind) attack Empire State University and fight Spider-Man, Sin-Eater crashes the battle. Sin-Eater shoots all four Lethal Legion members, taking Grey Gargoyle's petrification power and using it to immobilize Spider-Man. After the Lethal Legion members are imprisoned in Ravencroft, Norah Winters interviews Count Nefaria and learns that he is suddenly regretting his sins. When a riot occurs at Ravencroft, Nefaria informs Norman Osborn that Sin-Eater is coming for him.

Sin-Eater and his followers pursue Spider-Man and Osborn as the Order of the Web considers waiting for Sin-Eater to cleanse Osborn before intervening. As Spider-Man and Osborn escape underground, Sin-Eater catches up to them. As Spider-Man holds onto Sin-Eater to restrain him, Osborn activates an EMP to liquefy the floor beneath them. Despite Osborn's efforts, Sin-Eater catches up to him and purges his sins. Kindred arrives and apparently kills Sin-Eater, claiming that he had served his purpose.