Answer: muhammadali

AnswerCrossword Clue
MUHAMMADALIMegalomaniacal Athlete
MUHAMMADALI'60s and '70s heavyweight champ
MUHAMMADALISports Illustrated's Sportsman of the 20th Century
MUHAMMADALISports Illustrated's Sportsman of the Century
MUHAMMADALICassius Clay
MUHAMMADALISparking
MUHAMMADALISelf-proclaimed "astronaut of boxing"
MUHAMMADALI"It's hard to be humble when you're as great as I am" speaker
MUHAMMADALIWho said "My only fault is that I don't realize how great I really am"
MUHAMMADALISubject of the tome "GOAT"