快刀斩乱麻的英文：
[Literal Meaning]
sharp/knife/cut/messy/hemp
to cut the knot of hemp ropes with a sharp knife

[解释]
做事果断，能采取坚决有效的措施，很快解决复杂的问题。

[Explanation]
to solve a complicated problem by adopting effective measure

[例子]
如果你根本不想和他结婚，就应该快刀斩乱麻，早点和他分手。

[Example]
If you don't mean to marry him, you'd better solve the complicated problem by adopting effective measure and split with him earlier.

[英文等价词]
to cut the Gordian knot

He never procrastinates, but always takes resolute measures to solve a complicated problem in an instant.
他干什么事总是快刀斩乱麻，从不拖泥带水。

The cunning counsellors praise thee, because thou has cut the knots in which they have tied their own souls
老奸巨滑的大臣们赞颂你，因为你把束缚他们灵魂的症结快刀斩乱麻似地劈开了。