The query has provoked the reply. God is able to deliver anyone. The worst form of captivity comes from sin itself. Yet the purpose of the Atonement is to provide deliverance to all mankind. Nephi saw the Lord’s atoning sacrifice. He could, therefore, state with authority the Lord would “save thy children.” It doesn’t matter if the grip in which we find ourselves is from the “mighty” or “terrible,” the Lord will take the burden upon Himself. We will be “delivered.”
Nephi is talking about the Lord’s involvement in each of our daily lives. We can overcome the challenges and difficulties of life with His help. He is the perfect helper. He knows how to “succor” us all in our troubles, for there is nothing we face which He has not already faced. “The Son of Man hath descended below them all. Art thou greater than he?” (D&C 122:8.)