Who is Graal most Legendary Player?

[Scalper]

"legendary" is too loose of a term.

If you mean basically who was the person that almost everyone knew, It was definitely Chimp.

leg·end Pronunciation Key (ljnd)
n.

An unverified story handed down from earlier times, especially one popularly believed to be historical.
A body or collection of such stories.
A romanticized or popularized myth of modern times.
One that inspires legends or achieves legendary fame.

An inscription or a title on an object, such as a coin.
An explanatory caption accompanying an illustration.
An explanatory table or list of the symbols appearing on a map or chart.

But i can't really see how that applies to anyone in Graal.