Answer:
HMS Hood.
HMS Hood was a battlecruiser and was not intended to engage a battleship especially one such as Bismarck which was at that time the biggest battleship afloat along with her sister ship Tirpitz. Basically Battlecruisers engaged cruisers and avoided Battleships. Bismarck actually weighed in at 53,000 tons against Hood at 42,000. It seems logical that every ton on a warship is there for a purpose so a disparity of 11,000 tons could represent quite a lot of armour. Hood was scheduled for amongst other things having her deck armour improved.