Lehi saw the destruction and woe that would come upon his people if they did not repent. He also saw angels singing praises to their God. At the end of his vision, Lehi was overwhelmed with gratitude and reverence for the goodness of God. How? Where is the goodness in destruction? The key thing here, in the end, is that God is merciful because He will not allow those who come to Him to perish. Lehi not only saw the woe and the consequences of the inhabitants of Jerusalem and their leaders continuing as they were in disobedience, but he saw the grand promise given to those who would repent and turn from wickedness. After Lehi saw destruction and terrible things, he exclaimed, "Great and marvelous are thy works." First of all, he completely accepted what the Lord was doing. "Thy throne is high in the heavens; thy power and goodness and mercy are over all the inhabitants of the earth." Lehi’s focus from this point forth seemed to be on mercy. That is what his spirit saw in that vision—the mercy of God.
Book of Mormon Central, "What is it to Speak with the Tongue of Angels? (2 Nephi 32:2)," KnoWhy 60 (March 23, 2016).