This great destruction came in the form of wars, contentions, famines, and pestilences. This terrible destruction was one in a series of punishments. The people had previously fought in a war which decimated almost the entire society (Ether 9:12). This was followed by the dearth and plague of serpents (Ether 9:30-31). Both were devastating, but neither compared to what Moroni briefly discusses in this verse. It was a destruction so great as to be overshadowed only by their final, brutal annihilation.