In its first printing, the 1852 LDS edition introduced the plural destructions (“the Lamanites became frightened because of the great destructions among them”). This error was corrected in the second printing, perhaps as a result of checking the text against the 1840 edition. The plural destructions is theoretically possible, but usage elsewhere in the text shows that the plural here in Alma 43:39 is inappropriate (see the discussion under 1 Nephi 15:5).
Summary: Maintain the singular destruction in Alma 43:39, the reading of the earliest textual sources (including 𝓞).