The scathing verdict comes from Paolo di Canio, who was once banned from the Premier League for 11 matches for shoving referee Paul Alcock to the ground while playing for Sheffield Wednesday against Arsenal.
Di Canio - who has also drawn criticism in the past for his open fascist views and admiration of Italian dictator Benito Mussolini - was evidently disgusted at the performance of Balotelli during Euro 2012.
"Balotelli is just selfish. He deserves a lot of slaps," said Di Canio, who led Swindon to the League Two title this year in his first season in charge.
"Against Germany he did two good things but in the end I saw a player who was just waiting to celebrate.
"Balotelli does not play for the team, only for himself. He is an egotist, who thinks the world revolves around him.
"Guys like Balotelli deserve lots of slaps rather than pats on the shoulder. Antonio Cassano led the team to the final."
But a man much closer to the Italian team at the Euros painted a very different picture of the Manchester City striker. Andrea Pirlo, Italy's player of the tournament, praised the 21-year-old and said he would love to play alongside him at Serie A.
"Would I take Balotelli to Juventus? Of course I would take him," Pirlo said.
"I know how to talk to him because we both come from Brescia and when we are in the national team we speak in dialect.
"There was no problem with managing him in our dressing room. Indeed, he was very well-behaved."