Steff McKee is the main antagonist of the 1986 film Pretty in Pink. He is one of the arrogant so-called "richie" friends of Blaine McDonough, the other being Benny. He is not used to the main character, Andie Walsh, refusing to let him get with her. He is played by James Spader.
He poorly treats Andie Walsh, and it is because of his pressure that Blaine distances himself from her.
Finally, Blane defeats Steff by telling him off.