clincher /ˈklɪntʃə/

• 1. 

  N-COUNT A clincher is a fact or argument that finally proves something, settles a dispute, or helps someone achieve a victory. (能作为最终证据、解决争论或取得胜利的)事实 [非正式]

  例：

  DNA fingerprinting has proved the clincher in this investigation.

  DNA指纹已为此项调查出示了铁证。