Wiktionary
faithfullest
a. (en-superlative of: faithful)
Usage examples of "faithfullest".
But anon, as the two kings wist they were messengers of Arthur's, there was made no tarrying, but forthwith they spake with the knights, and welcomed them in the faithfullest wise, and said they were most welcome unto them before all the kings living.
Do you know that he’s the honestest and faithfullest fellow that ever lived, and that he has an irreproachable good name?