Answer: defeating

AnswerCrossword Clue
defeatingPrevent (an aim) from being achieved
defeatingDEFEAT, to win a victory over
defeatingReject or block (a motion or proposal)
defeatingWin a victory over (someone) in a battle or other contest; overcome or beat
defeatingRender null and void; annul
defeatingPrevent (someone) from achieving an aim
defeatingBe impossible for (someone) to understand