What is a single word, or phrase, for something that necessarily causes both harm and benefit? For example, a coal-fired power plant will harm human health through air pollution, but will bring electricity and economic development to a poor area.
Necessary Evil — Cambridge
noun Something unpleasant that must be accepted in order to achieve a particular result
"I think he regards work as a necessary evil."
"Most Americans accept taxes as a necessary evil."
That can sometimes be called a mixed blessing:
something that, although generally favorable or advantageous, has one or more unfavorable or disadvantageous features.
The word I think I would use would be disjunctive.
It means disjoined, or lacking connection/consistency. So it doesn't immediately speak of both benefit and harm, but if one words the rest of what one is saying appropriately it gives the desired meaning.
Nuclear power has disjunctive effects, both beneficial and harmful.
I found a relevant list of words and phrases, partial list is:
- mixed - partly good and partly bad
- patchy - if someone’s performance or work is patchy, it is good sometimes but not always
- two-edged - capable of being understood in two different ways or of having both good and bad effects
- spotty - only good, successful, or effective on some occasions or in some situations
- mixed blessing - something that has both advantages and disadvantages
- six of one, (and) half a dozen of the other - used for saying that two things are equally good or bad
- a double-edged/two-edged sword - a situation with as many bad qualities or effects as good ones
- work both ways - if something such as a particular situation or type of behavior works both ways, it has equal advantages and disadvantages for everyone it involves
- cut both ways - if something cuts both ways, it has both good and bad aspects
(Source: Macmillan Dictionary)
Maybe no pain no gain. That something beneficial (gain) is unachievable or unreachable without dealing with some harm (pain) as a side dish.
Paradox - something (such as a situation) that is made up of two opposite things and that seems impossible but is actually true or possible
: someone who does two things that seem to be opposite to each other or who has qualities that are opposite
: a statement that seems to say two opposite things but that may be true
I think you mean:
Meaning 1: Outstandingly Bad (Can take as Harm contextually)
Meaning 2: Remarkably Good (Can take as Benefit contextually)
Example: A coal-fired power plant is egregious in a way that one side when it is uplifting the economy of the area, other side it is downgrading the environment.
Already having supplied an answer to this question, it has just occurred to me that the metaphor you may be seeking is * a curate's egg*.
As the Oxford Dictionary Online explains it is British, meaning 'a thing that is partly good and partly bad': this book is a bit of a curate's egg.
ORIGIN early 20th century: from a cartoon in Punch (1895) depicting a meek curate who, given a stale egg at the bishop's table, assures his host that 'parts of it are excellent'.
Slightly tongue-in-cheek alternative:
... if the context is "a bad or unhealthy habit (such as an addiction to smoking)" - Wikipedia.
Smokers are aware of the harm but continue the habit due to their own perception of the benefit.
The closest to a single word we have for the concept would be "catch-22"
- a frustrating situation in which one is trapped by contradictory regulations or conditions.
- any illogical or paradoxical problem or situation; dilemma.
- a condition, regulation, etc., preventing the resolution of a problem or situation; catch.
It's derived from the novel of the same name.
In your example. "Civic engineers faced a catch-22 when it came to the coal plant. It would allow them to deliver energy cheaply to the area, but at the cost of added pollution"