Muhammad Ali was the first boxer to achieve which unprecedented feat in the lineal World Heavyweight Championship?

💡 Explanation:

Muhammad Ali became the first boxer in history to win the lineal (undisputed) World Heavyweight Championship on three separate occasions. His victories were in 1964 (against Sonny Liston), 1974 (against George Foreman in the 'Rumble in the Jungle'), and 1978 (against Leon Spinks). This unprecedented achievement is a key part of his historical significance.