Suppose that long ago, prior to the dawn of recorded history, the Earth was visited by an advanced extraterrestrial race, and a portion of humanity was carried away to the stars and deposited on an Earth-like world. Since then, each portion of humanity, both here on Earth and on that other world, have developed separately and free of further influence from the advanced aliens.
Now, an exploratory team from Earth encounters the other branch of humans, and at first contact, the alien race that separated us promises to use their technology to advance one branch of humans–but only one–into godlike beings. Both the people of Earth and of the other planet, of course, claim the prize, and a long and bloody war is waged. For generations, humans fight against other humans for the prize of apotheosis across the stars.
Your entire family is killed in the battle. Terrible atrocities are committed by the other branch of humanity–perhaps by your own as well, you cannot be sure of anything when your news reports come from your government. Every major catastrophe in human history, including the Holocaust, seems minor in comparison to the least of the atrocities committed by the enemy in their pursuit of godhood.
After a conflict of such duration that none alive remember peace as anything more than a beautiful myth, the war hinges upon the outcome of a single battle–you vs. a champion from the other branch of humanity. Whoever wins this one-on-one battle will be able to win the war, and attain godhood for their people. You cannot see your opponent–both of you are using some form of combat vehicle, (tank, fighter, mecha, whatever suits your imagination)–and your match carries on for a seeming eternity. At several points, you escape death at your opponent’s hands by a hairsbreadth, and miss numerous chances at victory by a similar margin.
Finally, you see your chance to strike, and do, disabling the enemy craft. The cockpit shatters, and you finally see your opponent: A ten-year-old child.
You have disabled the enemy craft. The child is helpless before you.
Do you strike, and assume god-like powers for yourself and your people, at the price of having the blood of a helpless child on your hands, or do you withhold your attack, granting godlike powers to the enemy and perhaps dooming your entire race?