undoing
/ˌʌnˈduːɪŋ/noun
in sing.
1- a person's ruin or downfall毁灭; 垮台; 崩溃：
he knew of his ex-partner's role in his undoing.
他知道原来合伙人在自己失败中扮演了何种角色。
1.1
- the cause of such ruin or downfall毁灭（或垮台、崩溃）的原因：
that complacency was to be their undoing.
那种自满将是他们失败的原因。