[ywjames]

I would say shoeless joe Jackson.
He was banned because of "suspicion in gambling."
However, no one can really prove that he gambled.
During the series Jackson had 12 hits (record) and a .375 batting average, leading individual statistics for both teams. He committed no errors and threw out a runner at the plate.

A side story

Ty Cobb and sportswriter Grantland Rice went into the liquor store Joe Operated after being banned from baseball. Jackson showed no sign of recognition towards Cobb. After making his purchase, the not so happy Cobb finally asked Jackson, "Don't you know me, Joe?" Jackson replied, "Sure, I know you, Ty, but I wasn't sure you wanted to know me. A lot of them don't."

A player like him shouldn't end his career and life like this.

I hope baseball don't make the same mistake with Pete Rose.