The Shliach Tzibur reads most prayers quietly until (about) the last verse, and then reads the last verse out loud (either for the congregation to follow along, or for them to answer Amen). Should the Chazzan finish the paragraph quietly to himself before repeating the last verse out loud, or should he say the last verse out loud as he arrives at that verse, without repeating it.
I would think repeating verses wouldn't be ok, since according to Bruchos 14a-b, when davening, one should not repeat words (aside from times you make a mistake and need to repeat the prayer again), however this may not apply to a Shliach Tzibur who is expected to say those verses out loud.