I missed the post-treble part of this thread.
Pre-treble, I think Vampeta (now coach of Gremio) was possibly the worst Inter transfer of all time. He arrived in 2000, played a game for us and somewhere along the way decided that he wanted to return to Brazil for vacation and never came back. If I am not mistaken, he wanted to be in Rio de Janeiro for Carnival.
There have been some real shit kickers at Inter since the Treble. Some of the players, such as such as M'Vila, Kharja, Palombo, Montoya, Taider, and Ansaldi are absolute contenders but my money is on either Kondogbia, Barbosa or Ciao Mario simply because of the amount of money spent on those players and what we got in return in terms of output and performances.
Lastly, I have saved a special word for Álvaro Pereira. He was a real Shit Cunt. I have no idea how he ended up at Inter. I do not think I have cursed an Inter player as much as I cursed him. Up until reading this thread, I had managed to erase him from my collective memory but this thread has brought it all back. Complete fuckn shit!