Hi,
the WW1 one under Werner...
As commander of U-55, after sinking the armed 5,597 ton steamer "Torrington" on 8 April 1917, he submerged with 34 survivors on deck, taking only the ship's master POW back to Germany--to bear postwar witness against him.
Werner then did the same thing with crew members of the torpedoed armed 3,066 ton steamer "Toro" on 12 April 1917, murdering 14 crewmembers in the same way, while carrying the Master and ship's gunner back to Germany as prisoners-- and witnesses.
Werner also torpedoed the fully lit and legally identified (but luckily, apparently empty of any but the crew) hospital ship "Rewa" on 4 January 1918, sinking it with a loss of only 4 dead. In what had become an evil pattern of homicidal and deliberately criminal behavior, AGAIN torpedoed a fully lit hospital ship, the "Guilford Castle" on 10 March 1918-- which did not sink only because one torpedo was a dud and the other he fired missed.