In my opinion, the "coldest" line in The Godfather was said by Michael Corleone, towards the end of the movie when he is in Las Vegas, before he offers to "buy out" Moe Green. Fredo Corleone tells Michael that "Moe loves the business," and Michael replies "Yeah -- well I'll make him an offer he can't refuse." That one line had potential for murder, and I knew Moe Green, whoever he was, was going to be murdered if he didn't accept Michael's "offer."