Marat Safin and The Williams Sisters hit the hardest and heaviest. I spent the last 1 hour and 30 minutes of boringness going through Point Tracker for the French Open and Wimbledon and here are my findings: Marat Safin averages 60-70 MPH on his winners. Obviously he doesn't force his power all the time and doesn't play the brawling power game the WTA tour does. Venus Williams averages 70-80 MPH on her winners. Believe it or not her forehand is hit harder than the backhand. Though that is quite obvious; her forehand is just isn't as consistant as her backhand. Serena Williams averages 75-85 MPH on her winners. The backhand is usually around 80 MPH while her forehand is somewhere in between. Sometimes it goes even higher. I don't believe all the crap some posters are saying here that Henin hits the ball hard. Some idiot even posted stupid numbers without even doing research; he said Henin hits between 80-90 MPH (ATP range)... Here is what I found on Henin: Her backhand winners clock in at 50-65 MPH and her forehand is 55-60 MPH on average. End of discussion, Henin fans; its obvious you cannot swallow how Henin is not the best at everything.