Shooting a severely wounded or unconcious man laying on the ground is indeed in cold blood. You may or may not believe it’s justified, but it’s done for cold-blooded reasons of practicality, not in the heat of battle or in self-defense.
What would you do?
Its a good question. However if things are that bad I certainly won’t be bringing the enemy into my home, nor expending priceless materials to save them.
Perhaps you give them a trial on the spot and sentence them accordingly.
If someone approaches peacefully they get peace. If they approach in a hostile manner they’ll get a piece of lead going real fast.
SHOOTING an unconscious or gravely wounded person is your FIRST mistake. You’re wasting ammo at that point. And if it’s truly a SHTF survival situation, you strip them first, before slitting throats. Clothing and equipment are valuable, attackers are not. . . It’s cold, but if things are that bad, a whole lot of the niceties of civilization will be put aside. . .
In post #13, your scenario stated they were "attackers" that were shot down. Attackers are the enemy. As you move across the objective, you cap each in the head so they aren't able to shoot you in the back as you continue to survey the area. It's not cold blood, it's survival. They attacked, they paid the price.
Think about it. If they are trying to kill you, do you really want to give them another chance? You might want to spend some more time on the range if necessary so as to kill them with one shot, not just wound them.