“Rocket” Rod Laver was the only man in history to win all four Majors (”Grand Slam”) in the same calendar year twice (1962 and 1969). Don Budge did it once in 1938. No one else has done it even once in the same year. Agassi never won three Grand Slam tournaments in the same year.
Agassi got a career grand slam — the only men’s player to do so since Rod Laver. The most Agassi won in one year was three.