From death unto death (εκ θανατου εις θανατον). From one evil condition to another. Some people are actually hardened by preaching.

And who is sufficient for these things? (κα προς ταυτα τις ικανοσ?). Rhetorical question. In himself no one is. But some one has to preach Christ and Paul proceeds to show that he is sufficient.

For we are not as the many (ου γαρ εσμεν ως ο πολλο). A bold thing to say, but necessary and only from God (2 Corinthians 3:6).