Pay attention to the punctuation and context.
In verse 1, Nephi just got done explaining that God is mightier than Laban and his fifty or even his tens of thousands. He testified of God's power with the Egyptians. He then testified that God will deliver them from Laban. In that context, he pointed out God's power to "destroy" Laban.
The punctuation then tells us that it was not "us" that would destroy Laban. Parallel structure through the use of the word "to" indicates that Nephi is saying,"The Lord delivered our fathers and He destroyed the Egyptians (after the children of Israel fled). Therefore, the Lord is able to deliver us and destroy Laban (after we have fled)."
Remember that Lehi already proph