necessary evil
US /ˈnɛs.əˌser.i ˈiː.vəl/
UK /ˈnɛs.əˌser.i ˈiː.vəl/
1.
something unpleasant that must be accepted or done in order to achieve a particular result
:
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Paying taxes is a necessary evil if we want public services.
•
For some, working long hours is a necessary evil to achieve financial stability.