This is not a review, the movie had enough of those, this is just a thought. Apparently what people expect from their superheros nowadays is ability to sacrifice millions 'for the sake of saving billions' and the superheros who refuse to go alone with that scheme must be killed (and they are in the movie). I think the director is counting on securing support of an average movie-goer, selling him on the idea that sacrificing a small number of people is just fine as long as the majority supposedly gains from it.
Of-course the entire concept is nonsense, there can be no beneficial murder. Sacrificing a minority for the benefit of a majority is not a virtue, it is a crime against individuals and their rights. Also while believing that world's super-powers (the countries with nuclear potential to destroy the planet) would cooperate against a common enemy is somewhat sound, believing that such a truce would be long lived or would lead to a more stable situation is nonsense. Power will not be shared and it only takes a little time before the old enemies are at each other's throats again. Of-course there is an added level of 'benefit' that their major cities are destroyed, which cannot make political or economic situation more stable, it would however achieve the exact opposite result.
If the Ozymandias (Adrian Veidt) wanted to increase stability in the world and achieve some for of higher cooperation among enemies, given his insight into limitless power he could have fairly easily achieved this goal by supplying the world with huge amount of very cheap energy. He could set up multiple corporations around the world selling the energy so cheaply, first he would put many 'old world' energy companies out of business but then he would provide enough energy for many new forms of businesses to be created. Cheaper food production and manufacturing, cheaper shipping, cheaper communications. Everything that he could do with the power and he chooses to pursue his idea of playing out the dreams of another murderer from history - Alexander the Great.
If after watching this movie an average person is left with an impression that it is an acceptable thing to do, to sacrifice minority for the benefit of majority (even if it means ideas based around grandiose totalitarian utopia and even when it is masked with a supposed formula for survival) then the director has done his job in cementing more of this collectivist ideology of central planning, the anti-humanist idea that anything goes as long as the technocrat can sell it as if it is done "for the greater good".
The greatest crimes on this planet were committed by people promising to ensure "the greater good". The future of such crimes is not behind single individuals, it is behind the mob, voting completely democratically to bring about yet another totalitarian regime. A regime that would take care of the mob by making a beneficial sacrifice of a small number of people (and small number of people would always lose in a democratic elections, thus the definition of mobocracy).
From murder of millions to "save billions" in the super-hero movies to taxing the few wealthy 1-2% apparently to ensure economic prosperity of everybody else. It doesn't work in the movie and it doesn't work in real life. It's not good morality and it's not good economics, but it makes a great show and sounds good in politics.