No doubts for me, he's quite easily our worst ever transfer. Di Maria, while he is a complete twat, still contributed to 4 goals and 12 assists in 2017 minutes. That's a contribution every 126 minutes under a manager who had no idea what to do with him our any of our attack for that matter.
Sanchez however scored 5 and assisted 9 in 2781 minutes. A contribution every 199 minutes. So statistically he was worse. But financially he blew our wage structure to bits, he was hyped far more than Di Maria and his arrival fecked Martial so bad he almost left the club. And to be frank, I'm going to remember Di Maria's goal v Leicester (that we bloody lost anyway) than anything Sanchez has done for us.
The only redeeming factor Sanchez has over Di Maria was that he at least seemed like a nice guy.