extreme: of the greatest possible degree or extent or intensity; "extreme cold"; "extreme caution"; "extreme pleasure"; "utmost contempt"; "to the utmost degree"; "in the uttermost distress"
the greatest possible degree; "he tried his utmost"
last: highest in extent or degree; "to the last measure of human endurance"; "whether they were accomplices in the last degree or a lesser one was...to be determined individually"
farthermost: (comparatives of `far') most remote in space or time or order; "had traveled to the farthest frontier"; "don't go beyond the farthermost (or furthermost) tree"; "explored the furthest reaches of space"; "the utmost tip of the peninsula"
HMS Utmost was a British U class submarine, of the second group of that class, built by Vickers Armstrong, Barrow-in-Furness. She was laid down on 2 November 1939 and was commissioned on 17 August 1940. So far she has been the only ship of the Royal Navy to bear the name Utmost.