What name was written on the forehead of the woman sitting on the scarlet beast?

Answer: Babylon the Great

On her forehead was written: BABYLON THE GREAT, THE MOTHER OF PROSTITUTES AND OF THE ABOMINATIONS OF THE EARTH.

“And on her forehead a mysterious name was written: BABYLON THE GREAT, THE MOTHER OF PROSTITUTES AND OF THE ABOMINATIONS OF THE EARTH.”— Revelation 17:5 (BSB)