Here is a list of large passenger ships lost over WW2 as a result of enemy action.

Hostilities – World War 2
This includes all large passenger ships (10,000 tons and over) that were lost as a result of hostilities during the
Second World War. It excludes passenger ships that were lost during the war from causes other than hostilities. It also excludes passenger ships that were lost after they had been converted into armed merchant cruisers, or other types of vessel. It does however, include passenger ships acting as troop ships and hospital ships.

World War 2
The world passenger ship fleet suffered the loss of 144 vessels through hostilities during in the six years of the
Second World War. This was more than the entire peacetime losses for all reasons in a century. A further 30
passenger ships that were converted into naval vessels were either sunk, or retained for military duties. Over
three times as many large passenger ships were lost in World War 2 than were sunk in the four years of World War 1

1. The main reasons for this carnage were: -

a.. The much greater geographical spread of hostilities in WW2 

b.. In WW1 passenger ship losses were largely confined to the Allies; in WW2 both sides suffered 

c.. Aircraft joined submarines as the major attackers. Once again surface warships were largely irrelevant as predators on the merchant fleets.

d.. Many more passenger liners played an active part in directly transporting troops to the battlefields and rescuing refugees from hostilities 

e.. Many passenger ships were sunk in home ports during air raids

f.. Germany’s conquest of most of continental Europe provided an effective launch pad for submarine and aircraft attacks on ships in the Atlantic and Mediterranean 

g.. Japan’s failure to organise a defence against US submarine attacks, resulted in the loss of all bar one ship in its passenger vessel fleet 

h.. The destructive effect of advances in military technology 

i.. From 1941 onwards Germany carried out unrestricted attacks on passenger vessels

Empress of Britain ablaze off Ireland.

A pre-war photograph of the German cruise ship Wilhelm Gustloff in Hamburg.
Astern of her is the liner Cap Arcona.
Both ships were sunk in 1945 with a combined loss of over 16,000 lives.

During the war the Allies lost 15,619,853 GRT of merchant shipping of all types. Japan lost 8,141,591 GRT of its
shipping. The intensity of the submarine war can be gauged from the following statistics: -

Germany commissioned 1,149 U-boats plus 21 captured units, giving a total of 1,170, compared with 343 in WW1. During WW2 630 U-boats were lost in action, 81 were lost in harbour because of air attacks, 42 lost in
accidents, 38 were written-off because of severe damage and 11 were interned or taken over by other countries
(including 4 by Japan). The total losses were therefore 802, leaving 368 survivors, of which 215 were scuttled
at the end of the war on the orders of Admiral Dönitz.

USA commissioned 262 submarines of which 52 were lost. US submarines were largely employed in a highly
successful campaign against Japan. The US submarine construction programme was wound down towards the end of
the war, as there were virtually no Japanese ships left in service.

USSR had 210 submarines in service at the outbreak of the war, but only completed a further 29 during the war because its shipyards were captured by Germany. During the war USSR lost 109 boats.

UK commissioned 220 submarines and lost 75.

Italy commissioned 172 submarines and lost 82.

Note: Ships are grouped in the above table by the year of their loss; they are not arranged in chronological order of sinking within each year. The “Casualties” figures in the table are in many cases not available or are merely approximate numbers.

The U-Boat Captain Lempe who sank the liner Athenia on day one of WW2. remained in the German submarine service and went on to be promoted to the rank of Kapitänleutnant. He was awarded the Iron Cross (First Class) in January 1940 and the Knight’s Cross of the Iron Cross in August of that year.

Kapitänleutnant Lemp & Admiral Dönitz

 Lemp lost his life when in command of U-110, which was  captured on 9 May 1941 south of Iceland by the destroyers HMS Bulldog, HMS Broadway and the corvette HMS Aubretia. After being forced to the surface by depth charges,  and then shelled, Lemp ordered the crew to abandon ship but was not among the 34 survivors rescued by the British warships.

Cunard liner Lancastria.

City of India sinking off Oran.

 I must acknowledge my debt to URL:
http://www.shipsnostalgia.com/guides/Passenger_Ship_Disasters_-_Part_7 for a great deal of this information.