Stephen

Take a look at Acts 6:15, where Stephen, at his trial, had a face of an angel. Now consider what Scripture tells us angels say when they appear to us:

Fear not.

And then consider that, confronted with a visage like that of one of His mighty messengers, the Sanhedrin still dared to murder him. If we wonder whether a direct sign from God will convert a man apart from the "heart tenderizing" ministry of the Holy Spirit, wonder no more. Just like Israel ignored Moses' staff, Elijah's fire, and the Resurrection, they ignored Stephen's angelic face, too.