The 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.

[11] As Mother Superior, she was the leader of a group called the Sisters of Sin, young orphan girls who were accelerated into adulthood and given psionic powers by the Red Skull after being indoctrinated by Sinthea.

After the Red Skull was seemingly assassinated by the Winter Soldier under Aleksander Lukin's orders, Crossbones broke into the facility, kidnapped her and tortured her to break the reprogramming.

[16] She delivers a video to the media recorded three months before Barnes's trial, declaring that the reformed hero was not brainwashed, but was an accomplice and fully aware of these actions.

[volume & issue needed] She, along with Master Man, is later seen on Ellis Island where she pretends to blow up the Statue of Liberty with Falcon and Black Widow bound and gagged inside, unless Barnes is delivered to her.

Thor manages to kill the Serpent and Odin strips the Worthy of their hammers, causing Sin to lose Skadi's powers.

[20] Sin later returns as one of the villains working alongside Zemo as part of a plot to forcibly sterilize the human race.

She battles Captain America (Sam Wilson) and apparently falls to her death after refusing to allow the hero to save her from an explosion.

[25] In Rügen, Sin attacks a group of archaeologists and steals from them the helmet of Erida, imbuing her with the power to manipulate hatred and rage.

Captain America, Photon, Shang-Chi, and Wasp of the Avengers Emergency Response Squad arrive to confront Sin, who had been using her new powers to send the locals into a mindless rage while empowering herself with their generated hatred.

Sin is eventually stopped when Photon strikes her helmet at lightspeed with Captain America's shield, causing her to disintegrate.

[26] Sin appears to have no superhuman abilities but being trained by her father, the Red Skull, through which she is an expert hand-to-hand combatant and martial artist.

As Mother Superior, Sin possessed a range of superhuman powers including telepathy, telekinesis, teleportation and intangibility.

[27] A character loosely based on Sinthea Shmidt / Sin named Valentina de Santis appears in Captain America (1990), portrayed by Francesca Neri.