Angel Di Maria
A bit of strange one this. The Argentine was very successful at Real Madrid and has continued to have a good career at Paris Saint-Germain after he left at Old Trafford.
However, after joining United for £59.7m in 2014, Di Maria never really settled in England, scoring just four goals in 32 appearances for the Red Devils. He may not have been the worst purchase, but the disappointment was larger as a lot more was expected of him following such a substantial transfer fee.
