By deliverance, Nephi probably means the Lamanites’ return of Nephite lands after being converted. Although the more typical form of deliverance in the past had been in battle, this deliverance also qualifies as a blessing from Yahweh. Nephi had been intimately involved in the mass Lamanite conversion; therefore, he understood its connection with Zarahemla’s being returned to the Nephites.
Nephi’s specific catalogue of sins (v. 21) is directed against the secret combinations, suggesting that his audience understood what he was talking about. Certainly Gadiantons were present (Hel. 8:1), but it seems probable that the existence of secret combinations was well known, even if the particular oaths were not. The Gadiantons were, after all, a political party who dominated the government. It would be surprising if the rest of the people did not know at least generalities about them. Part of the reason that some modern readers assume that the Book of Mormon’s secret combinations were based on Freemasonry, contemporary with Joseph Smith, is that the Masons and their secret oaths were well known, even without specifics on the content of their ceremonies. In this same way, the Gadiantons were hardly a secret organization, even though they did have secrets in the organization.
(For Nephi’s accusations of “murder,” plundering, stealing, “bear[ing] false witness… and… all manner of iniquity,” see the commentary accompanying Alma 17:14, 50:21, and Helaman 6:17.)