This change of the preposition unto to into in the 1849 LDS edition seems to be a typesetting error. Its probable source is the into in the immediately preceding prepositional phrase (“into captivity”) which is conjoined with “unto destruction”.
Elsewhere in the Book of Mormon text, we have 18 occurrences of unto as the preposition for destruction but never into. On the other hand, captivity has only into (14 times), never unto. So the mixed use of prepositions in 1 Nephi 14:7 (that is, “into captivity and also unto destruction”) is precisely correct. The 1849 edition created a unique and incorrect reading.
Summary: Restore in the LDS text the original preposition in 1 Nephi 14:7 (“unto destruction”); unto, not into, is what the text systematically uses with the noun destruction.