Which tennis player won a major tennis championship in singles, Juan Martín del Potro or Bob Bryan?
Juan Martín del Potro:  His biggest achievement has been winning the 2009 US Open, defeating Rafael Nadal in the semifinal and 5-time defending champion Roger Federer in the final. Bob Bryan:  He has won twenty-three Grand Slam titles: 16 in men's doubles and 7 in mixed doubles.
i don't know