adjective
eviler; evilest
[or more ~; most ~]
morally bad
causing harm or injury to someone
marked by bad luck or bad events
very unpleasant or offensive
showing that something bad will happen
noun
plural evils
[noncount] :the force of things that are morally bad
[count] :something that is harmful or bad - usually plural
The lesser of two evils or the lesser evil is the better choice between two unpleasant choices.
A necessary evil is a bad or unwanted thing that has to be done or accepted to achieve some good result.