If someone intentionally does evil then I should not exert power, if I have it ,over him, I cannot force him to do what I think is good. I cannot anybody Force to do my will even if I believe it to be good and his doing evil. it always has to be a dialogue. What if a terrorist wants to do evil and kill a hostage? Then I may destroy evil but not with the aim of killing the terrorist. it always should be a dialogue and if the dialogue is not possible and I cannot talk to the terrorist to see if he is doing evil, tham I can shoot him in order to destroy evil but not in order to kill him. No one is an absolute reification of evil, I can never consider someone’s Life a Pure Evil but I can destroy evil by not letting someone hurting others- if I believe such hurting is evil. in the movie American Sniper that is a scene where kids are playing with an RPG and the sniper is in a dilemma whether it is necessary to shoot them in order to protect a convoy .in the end it always depends on an individual conscience. If I believe something to be evil then with a clear conscience which is in my view given by God I must choose . the theory of a lesser evil does not seem necessary. Both sniper and kids make believe that they are doing a good thing , right thing, protecting Country .concretely we can never say who is doing a good thing but the choice between two evils is not possible. I can either choose good or evil. If I believe that it is the right thing to protect the Convoy then I must be ready to destroy any evil which may endanger it. Nevertheless it always should be my choice, not choice of someone above me as for example the case of soldiers.