Would You Kill Someone You Love for the Good of Mankind?

I have my X aura about me again, which is what this question is a reference from.

There are no consequences or anything, it is just one simple question with no specified story. To an extent this is just an "X", end of the world question. Just simply; would you kill someone dear to you to keep the world as it is now, or would you not kill them and let the worlds' inhabitants die and hope for a revolution in the future?

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I am afraid to say that I would probably make perish my dear friend or family member to save the world. I know that they are close and that it would be difficult, but it is one life in return for millions. Unfortunetly I am just thinking about numbers here and not the love I have for people close to me. Also, letting the world die for the sake of killing your friend would be selfish, but there would be no one left on the world to complain.

Remember, I do not bother of the plot holes in the question. If there is little understanding then either watch or read Clamp's "X" series/movie or just do not answer at all. I just want honest and simple answers and explanations.