#10. Kaka (2009) £56 Million
Arguably the transfer that can be termed as the biggest flop out of the 10 mentioned above, Kaka was at the peak of his career at AC Milan when Real Madrid came knocking with £59.7m and neither the Italian club nor the Brazilian could not say no. After a decent first season, Kaka failed to cement a permanent place in the side and was eventually sold back to AC Milan for, wait for it, ‘Nothing’. Kaka’s career went downhill ever since he moved to Real Madrid and in many ways, the transfer that was regarded as ‘a great buy’, turned out to be a nightmare for both parties.