It would be a lot of fun to attack a late war Yamato class BB.
150
!!! 
25mm AA guns, plus 24 5" multipurpose guns.
The thing would be a death wagon to any airplane that attacked it without an organized mission and a LOT of aircraft backing it up.
Bismark would, on the otherhand, be comparatively easy. The Europeans just didn't overdo the AA guns like the USN and IJN. The Bismark also loses 30,000 tons to the Yamato, which translate directly into durability.
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Sisu
-Karnak