That's a loaded question to me because technically no matter how good they played, they weren't good enough to win THAT game because they couldn't win over THAT jury.
But anyways for me it's probably Amanda when she lost to Parvati in FvF1. I mean the fuck up of there being 8 jury members and a Final 2 contributed to this, so someone had to get 5 votes even though I think it likely would have been 4-4, and Amanda played the better game anyways. Parvati is a good player and she did pull off some great moves but in this game I don't think Parvati could have made it to the FTC without Amanda but I think Amanda had a chance without Parvati.