1 Nephi 4

I don't have any problem with Nephi's slaying of Laban--it doesn't seem much of a moral quandary. So I'm not going to discuss it.

Except to note that we get four reasons why Laban needs to be slain:

1. The Lord delivered him to Nephi to fulfill a righteous purpose: "better that one man should perish than that a nation should dwindle and perish in unbelief." (v. 12-13)
2. Laban tried to kill Nephi. (v11)
3. Laban wouldn't follow the commandments. (v11)
4. Laban had taken their property. (v11)

Later Zoram, Laban's servant, joins Nephi's party. After he gives his word, Nephi and his brothers no longer had any fears that Zoram would betray them. (v37)