The Spirit tells Nephi to kill an unconscious man, saying it's better for one man to die than a whole nation dwindle in unbelief.
And it came to pass that the Spirit said unto me again: Slay him, for the Lord hath delivered him into thy hands; Behold the Lord slayeth the wicked to bring forth his righteous purposes. It is better that one man should perish than that a nation should dwindleand perish in unbelief. 1 Nephi 4:12-13
Jesus encourages the Nephites to slaughter their enemies, like a lion among a flock of sheep.
Then shall ye, who are a remnant of the house of Jacob, go forth among them ... as a young lion among the flocks of sheep, who, if he goeth through both treadeth down and teareth in pieces, Thy hand shall be lifted up upon thine adversaries, and all thine enemies shall be cut off. ... And thou shalt beat in pieces many people; ... And it shall come to pass, saith the Father, that the sword of my justice shall hang over them at that day; and except they repent it shall fall upon them, saith the Father, yea, even upon all the nations of the Gentiles. 3 Nephi 20:16-20