Paul Pogba left Manchester United this summer, saying he wanted to show the club "they made a mistake".
The France midfielder, who is expected to rejoin Juventus on a free transfer, lifted the World Cup with his country in 2018 - but won only the Europa League and Carabao Cup at club level during his six-year second spell at Old Trafford.
His last three campaigns only produced eight goals.
But Pogba is far from being the only big name in Europe's major leagues with a point to prove this season.
From players who had disappointing loan spells to others who have barely played, who else really needs a big campaign?