Sin (Sinthea Schmidt) is a supervillain appearing in books published by Marvel Comics as the daughter of the Red Skull. Sin first appeared in Captain America #290 (Feb 1984), and was created by J.M. DeMatteis and Paul Neary.

Biography

Seeking an heir, the Red Skull (Johann Schmidt) fathered a daughter with a washerwoman. After the woman died in childbirth, the Red Skull angrily almost killed the child as it was a girl. But his follower Susan Scarbo convinced him not to, telling him she would raise the girl herself as her nanny. Red Skull agreed and left the girl now named "Sinthea Schmidt" with Scarbo to be raised by her and indoctrinated with Red Skull's views as she grew up. Red Skull returned when Sinthea was a child and put her in a machine that had her aged into adulthood and gave her superhuman powers.

As Mother Superior, she became the leader of a group called the "Sisters of Sin", young orphan girls who were accelerated into adulthood and given psionic powers by the Skull after being indoctrinated by Sinthea. The Sisters of Sin would have many run-ins with Captain America (Steve Rogers) before being de-aged when they entered a chamber designed to reverse Red Skull's aging process and they were restored to children (she would later claim she was deaged to the wrong age - but whether this is true, and in which direction, is unclear).

Later, Mother Night (Susan Scarbo) reformed the Sisters of Sin and became their new leader, while the deaged Sinthea herself took the name Sister Sin.

Sometime later, she was captured by S.H.I.E.L.D. and taken to their reeducation facility where they reprogrammed her with false memories as "normal" American girl Erica Holstein. After the Red Skull was seemingly assassinated by the Winter Soldier under Aleksander Lukin's orders, Crossbones broke into the facility, kidnapped Erica and tortured her to break her reprogramming. After he succeeded, she simply calls herself "Sin" while she entered into a relationship with him and the two went on a killing spree. She later reunited with Red Skull while her father was living inside General Lukin's mind.

As the first part of Red Skull's Master Plan, Sin disguised herself as a nurse after the Civil War while Crossbones sniped Captain America at the courthouse, even though it meant obeying her father and abandoning Crossbones to his fate. Sin then revealed to Sharon Carter that Carter was the one who had killed Cap. Now the leader of a new incarnation of the Serpent Squad, Sin breaks Crossbones out of jail. He is later apprehended again, and Sin wounded in an attempt to break into the Capitol Building. Sin is later sent to assassinate the Democratic and Republican presidential candidates, but is stopped by the new Captain America (Bucky Barnes). In the aftermath of Captain America: Reborn, after attempting to put her father in Steve Rogers's body, she is injured by the explosion of her father's mechanical body and her face is hideously scarred like her father's.

She is later visited in prison by Baron Zemo for information about Bucky. Sometime later, Master Man sprung Sin from prison, prompting Sin to take her place as the new "Red Skull". She delivers a video to the media recorded three months before Bucky Barnes's trial where he declares that he wasn't brainwashed but was an accomplice and fully aware of his actions. She along with Master Man are later seen on Ellis Island where she pretends to blow up the Statue of Liberty with Falcon and Black Widow inside, unless Bucky is delivered to her.


"Fear Itself"
During the Fear Itself storyline, Sin, with Baron Zemo's help, unearths the Hammer of Skadi and becomes Skadi in order to free the Serpent, God of Fear, from his underwater prison. Sin vows to do what her father failed to do in taking over the world. She succeeds in her mission in freeing the Serpent and then prepares an army of Nazis to take over the D.C. Capital. During their battle in Washington, D.C., Skadi mortally wounds Bucky Barnes (still serving as Captain America). In the final battle, Skadi battles Steve Rogers. Thor gives Rogers his hammer Mjolnir so that he can make up for the loss of his shield. Thor manages to kill the Serpent and Odin strips the Worthy of their hammers, causing Sin to lose the power of Skadi. This leaves Sin incapacitated.


All-New Captain America
Sin later returns as one of the villains working alongside Baron Zemo as part of a plot to forcibly sterilize the human race. She battles Sam Wilson, the new Captain America, and apparently falls to her death after refusing to allow the hero to save her from an explosion.