Yes, he has 8 gold medals to his name and a total of 11 Olympic medals.
But to me, the Greatest Olympian title should only given to people who have been able to consistently perform well in the Olympics.
That being said, if he ever performs like this in the next Olympics, he would deserve the title indeed.
With that, I present you,
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* I am unable to credit this as I do not know who made this.
So whoever it is, my apologies.