Nah... if you are talking Fosun era then you look at the waste of money and come to that conclusion perhaps but "worst ever"... not even close.
I recall we signed a keeper from Leicester in the 90's and paid a lot for him ...never played, didn't get a visa off memory. If we're looking at things just under Fosun, then I'd say Wilian Jose was worse, Paul Gladon was worse, Silva was absolutely worse and we still haven't got rid of him. There's others as well...Johnstone, Trincao, Bentley, King, Bodvarsen, Gladon, Oniangue, King... the list is endless.
That said, 10 years ago we'd have given a lot to be in such a position where we could write off a few dud transfers. All history now, Guedes has gone, we move on. Hopefully it means a replacement is coming in.