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root of an evil; source of a problem; source of trouble; cause of misfortune
禍根を断つために早めに対処すべきだ。
We should deal with it early to cut off the root of the problem.
その判断が後の禍根となった。
That decision became the root of later trouble.
禍根を残さぬよう徹底的に解決した。
We resolved it thoroughly so as not to leave any trouble behind.