Mario.
He just had the wrong mentality.
Balotelli had all the enjoyment of playing football ripped out of him by getting racially abused evey week in Serie A as a teenager and then from the people who were supposed to be supporting him when he put on the Italian shirt.
Hard to imagine the psychological damage that being racially abused publicly every time you stepped onto a football pitch from the time you were 15 would do, but its absolutely no surprise that it turned him against football.
I think that makes him fundamentally different from a lot of the players on these lists. He had the mentality to succeed and then it got taken away.