The way I see it, in times of war there are casualties. In the instance of the Assyrians who got wiped out by an angel, had Jehovah not intervened the Assyrians would have raped, plundered and killed God’s people. Putting them to sleep was a very painless and merciful way to deal with the invaders. Same thing with the Ten Plagues. When a human leader makes bad choices his subjects will inevitably suffer. Look at the suffering and destruction Hitler brought on the German people. Pharaoh was stupid and stubborn and could have avoided bringing destruction upon himself and the nation. But even at that, the Bible says a vast mixed company went out of Egypt with the Hebrews – recognizing Jehovah’s superiority to the impotent Egyptian gods.
Keep in mind too, all those who have been put to death by God, either directly like, Sodom and Gomorrah, or indirectly, such as when God directed the Israelites to exterminate various nations, those people will come back.