The Losing Move. Usually used in the
context of playing a board game of
Go. But it can be used in just about any context you can
think of, which allows you to say that something is hopeless, despairing, unrealizable.
He thought that the move was good, it was actually the move playing which the eventual
loser still had his chances, but chose a clearly inferior
play which was Baizhao. The winner next made no mistakes so that even if the
loser didn't make any either, he still could not recover the loss.