Red Sonja the She-Devil with a Sword, although loosely based on Robert E. Howard's character Red Sonya of Rogatino, was created for Marvel Comics by Roy Thomas and Barry Windsor-Smith. Sonja first appeared in Conan the Barbarian #23 (Feb. 1973).
Red Sonja has become the female barbarian archetype; both fierce and stunningly beautiful, and who typically wears armor resembling a bikini. Her origin story, "The Day of the Sword", first appeared in Kull and the Barbarians #3 also written by Thomas, with Doug Moench and Howard Chaykin illustrating.
Red Sonja lived with her family in the Hyrkanian steppes (equivalent to modern Ukraine/Russia). When she had just turned 17 years old, a group of mercenaries murdered her family, burned down their home and she was brutally raped by the leader, who left her in shame. Answering her cry for revenge, the red goddess Scathach appeared to her, and granted Sonja incredible skill with swords and other weapons on the condition that she would never have sex with any man unless he first defeated her in fair combat.
Trivia: Elfquest creator Wendy Pini often appeared as Red Sonja at conventions during the 1970's in full chainmail bikini, as part of artist Frank Thorne's traveling wizard show. Wendy was one seriously hot chick as the sword-weilding Sonja.