Mormon 3

It is always interesting to me that the Lord doesn't immediately destroy the wicked but gives them every opportunity to repent for after so many defeats, the Nephites -

"did meet them again, and did beat them; nevertheless the strength of the Lord was not with us; yea, we were left to ourselves, that the Spirit of the Lord did not abide in us; therefore we had become weak like unto our brethren.
27 And my heart did sorrow because of this the great calamity of my people, because of their wickedness and their abominations.  But behold, we did go forth against the Lamanites and the robbers of Gadianton, until we had again taken possession of the lands of our inheritance."  (Book of Mormon | Mormon 2:26 - 27)

Thus allowing a ten year reprieve of war for repentance.  But it didn't happen, and after the Nephites -

"...began to swear before the heavens that they would avenge themselves of the blood of their brethren who had been slain by their enemies.
10 And they did swear by the heavens, and also by the throne of God, that they would go up to battle against their enemies, and would cut them off from the face of the land."  (Book of Mormon | Mormon 3:9 - 10)

At that point -

"...I, Mormon, did utterly refuse from this time forth to be a commander and a leader of this people, because of their wickedness and abomination."  (Book of Mormon | Mormon 3:11)

And the Lord told Mormon -

"Vengeance is mine, and I will repay; and because this people repented not after I had delivered them, behold, they shall be cut off from the face of the earth."  (Book of Mormon | Mormon 3:15)