Sinister Sphinx in the villainess in the 1948 comics Blue Beetle #56.
The Sinister Sphinx was a beautiful female assassin who began to target prominent women for murder and black-mail. Her plan was to kill these women and by leaving her calling card, a sphinx figurine, that when in the future she abducted women to extort money from their loved ones that they would remember her ruthless nature and pay as quickly as possible lest they lose their loved one.
The Sphinx's weapon of choice was a knife and she traveled in a souped-up roadster with a sphinx figure on the hood.
Her murders brought her to the attention of the Blue Beetle, his partner Mike, and his girlfriend, Joan Mason. Joan came up with the idea to create a fake crime scene attributed to the Sphinx by leaving a figure at the scene of the crime. Joan figured the Sphinx's pride would get the better of her and make the crook come out of hiding to confront the copycat. This plan was successful and Blue Beetle was able to apprehend the Sphinx though her true identity was never revealed.