Given the reference text about Rafael Nadal, tell me how many singles grand slam titles he has won, which grand slam tournament he has won the most, and the main strength of his tennis game.

Rafael Nadal has won 22 singles grand slam titles. The majority of his grand slam wins have been at the French Open, where he has won 14 times.

The main strength of his tennis game is his forehand because of his ability to hit the ball with extremely heavy topspin at difficult angles.