Whoso was found to commit iniquity, and three witnesses of the church did condemn them before the elders, and if they repented not, and confessed not, their names were blotted out. Moroni 6:7 9:35
Mormon writes another letter to his son, Moroni.
I'm writing somewhat to you again.
2 For behold, I have had a sore battle with the Lamanites, in which we did not conquer; and Archeantus has fallen by the sword, and also Luram and Emron; yea, and we have lost a great number of our choice men.
I had a sore battle with the Lamanites, who are always stirred up by Satan.
4 Behold, I am laboring with them continually; and when I speak the word of God with sharpness they tremble and anger against me; and when I use no sharpness they harden their hearts against it; wherefore, I fear lest the Spirit of the Lord hath ceased striving with them.
I preached non-stop to the Lamanites, but they trembled in anger or hardened their hearts against me.
I think the Spirit of the Lord is done striving with them.
6 And now, my beloved son, notwithstanding their hardness, let us labor diligently; for if we should cease to labor, we should be brought under condemnation; for we have a labor to perform whilst in this tabernacle of clay, that we may conquer the enemy of all righteousness, and rest our souls in the kingdom of God.
7 And now I write somewhat concerning the sufferings of this people. For according to the knowledge which I have received from Amoron, behold, the Lamanites have many prisoners, which they took from the tower of Sherrizah; and there were men, women, and children.
So I gave up on them, since they are such a loveless, blood-thirsty bunch of savages.
8 And the husbands and fathers of those women and children they have slain; and they feed the women upon the flesh of their husbands, and the children upon the flesh of their fathers; and no water, save a little, do they give unto them.
The Lamanites forced Nephite women and children to eat their own husbands and fathers.
9 And notwithstanding this great abomination of the Lamanites, it doth not exceed that of our people in Moriantum. For behold, many of the daughters of the Lamanites have they taken prisoners; and after depriving them of that which was most dear and precious above all things, which is chastity and virtue --
The Nephites raped the Lamanite women, taking from them that which was most dear and precious to them -- their virginity. 
10 And after they had done this thing, they did murder them in a most cruel manner, torturing their bodies even unto death; and after they have done this, they devour their flesh like unto wild beasts, because of the hardness of their hearts; and they do it for a token of bravery.
16 And again, my son, there are many widows and their daughters who remain in Sherrizah; and that part of the provisions which the Lamanites did not carry away, behold, the army of Zenephi has carried away, and left them to wander whithersoever they can for food; and many old women do faint by the way and die.
19 And they have become strong in their perversion; and they are alike brutal, sparing none, neither old nor young; and they delight in everything save that which is good; and the suffering of our women and our children upon all the face of this land doth exceed everything; yea, tongue cannot tell, neither can it be written.
The Nephites murdered the Lamanites in a most cruel manner, torturing them to death, nd eating their bodies after they died.
20 And now, my son, I dwell no longer upon this horrible scene. Behold, thou knowest the wickedness of this people; thou knowest that they are without principle, and past feeling; and their wickedness doth exceed that of the Lamanites.
22 But behold, my son, I recommend thee unto God, and I trust in Christ that thou wilt be saved; and I pray unto God that he will spare thy life, to witness the return of his people unto him, or their utter destruction; for I know that they must perish except they repent and return unto him.
24 And if it so be that they perish, we know that many of our brethren have deserted over unto the Lamanites, and many more will also desert over unto them; wherefore, write somewhat a few things, if thou art spared and I shall perish and not see thee; but I trust that I may see thee soon; for I have sacred records that I would deliver up unto thee.
25 My son, be faithful in Christ; and may not the things which I have written grieve thee, to weigh thee down unto death; but may Christ lift thee up, and may his sufferings and death, and the showing his body unto our fathers, and his mercy and long-suffering, and the hope of his glory and of eternal life, rest in your mind forever.
So they were even worse than the Lamanites.
26 And may the grace of God the Father, whose throne is high in the heavens, and our Lord Jesus Christ, who sitteth on the right hand of his power, until all things shall become subject unto him, be, and abide with you forever. Amen.