a stick to beat someone with
US /ə stɪk tə biːt ˈsʌm.wʌn wɪθ/
UK /ə stɪk tə biːt ˈsʌm.wʌn wɪθ/

1.
攻擊某人的把柄, 批評的藉口
a piece of information or an argument that can be used to criticize or harm someone
:
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His past mistakes became a stick to beat him with during the election campaign.
他過去的錯誤成了競選期間攻擊他的把柄。
•
Don't give them a stick to beat you with by admitting your weaknesses.
不要通過承認自己的弱點給他們攻擊你的把柄。