Helaman 10

The Lord told Nephi -

"...I have beheld how thou hast with unwearyingness declared the word, which I have given unto thee, unto this people.  And thou hast not feared them, and hast not sought thine own life, but hast sought my will, and to keep my commandments.
5 And now, because thou hast done this with such unwearyingness, behold, I will bless thee forever; and I will make thee mighty in word and in deed, in faith and in works; yea, even that all things shall be done unto thee according to thy word, for thou shalt not ask that which is contrary to my will.
6 Behold, thou art Nephi, and I am God.  Behold, I declare it unto thee in the presence of mine angels, that ye shall have power over this people, and shall smite the earth with famine, and with pestilence, and destruction, according to the wickedness of this people."  (Book of Mormon | Helaman 10:4 - 6)

I believe that most people would use this now granted power to destroy or punish the wicked.  But the Lord knew that Nephi would "not ask that which is contrary to my will"  The Lord's will is that all people repent and keep His commandments.  Even though Nephi had the power to punish, he did the Lord's will for -

"...he did stop and did not go unto his own house, but did return unto the multitudes who were scattered about upon the face of the land, and began to declare unto them the word of the Lord which had been spoken unto him, concerning their destruction if they did not repent."  (Book of Mormon | Helaman 10:12)