功败垂成

lit. to ruin the enterprise for the sake of one basketful; to fail through lack of a final effort

to waste all one's previous efforts (idiom); all that has been achieved goes down the drain

to give up halfway (idiom); leave sth unfinished

to succeed through failure; to achieve one's final aim despite apparent setback

to turn defeat into victory (idiom); snatching victory from the jaws of defeat

to miss narrowly; to let a great opportunity slip