​The Bible says, “If possible, so far as it depends on you, live peaceably with all,” and that is to be our desire and our practice. There are times, though, when this isn’t possible, for example when someone is threatening our life or that of a loved one; at this time the preservation of the innocent party takes precedence. That is to say, yes, the use of lethal force to defend yourself is approved by the bible’s teaching.
This does not mean that we are allowed to seek revenge or take “an eye for an eye.” That aspect of justice and punishment is the responsibility of the government, not the individual; and, ultimately, vengeance belongs to the Lord, whose knowledge is perfect, and whose judgment is just.  

​This question needs to be answered in two parts, what happens to us when we die, and what will happen at the return of the Lord?
When we die our bodies turn to dust (or ash), but our souls, which do not die or sleep, go immediately to the place of their eternal habitation; either to behold the face of God in heaven or to suffer punishment in hell.
Both of these eternal destinies are set when we die, we having rejected or received Christ by faith, but will take on a greater dimension on the last day, the day of judgment of which the Bible clearly speaks.
On that day God will raise and recompose the bodies of all who have ever lived, rejoin them with their immortal souls, publically pronounce a perfectly just and righteous judgment, and send each one, body and soul, to their eternal destiny, heaven or hell.