Sunderland have been forced to pay Inter Milan a sum of €10.5 for the loan transfer of Ricardo Alvarez back in September 2014.  The Argentine international who joined the English side temporarily played 11 times and scored once after struggling with a knee injury.
The clause inserted in the deal meant Sunderland would go on and purchase the player because the Black Cats avoided relegation to the Championship.
Sunderland argued that they did not need to pay the amount because they had signed a player who needed knee surgery. 

Both clubs took the matter to the Centre for Arbitration for Sport (CAS)  and the final verdict is that Sunderland must now pay Inter €10.5 million.
After both teams refused to sign Alvarez, he eventually joined Sampdoria in January 2016.