make a clean break with 一刀两断

“一刀两断”，汉语成语，字面意思是一刀斩为两段（cut in two with one stroke of the knife），比喻坚决断绝关系。可以翻译为“make a clean break with，break off all relations with”。

例句：

与家庭一刀两断

Cut the knot from the family; break off all relations with the family

我们必须与旧思想一刀两断。

We must make a clean break with old ideas.