They were just as helpful as the cruisers and destroyers, they all lent a helping hand; but World War 2 could have been won without battleships.
Battlewagons were great for shore bombardment duties, but they themselves made great targets for airplanes (HMS Prince of Wales, IJN Yamato, IJN Musashi, USS Arizona, USS Oklahoma, USS Utah, were all sunk by planes).
During WWI, battleships made a dismal showing for any surface actions fought.
The only action modern steel battleships ever fought as designed to do, was at Tsushima in 1905.
A few scuffles here and there (Atlantic, Med, and Pacific) but no decisive fleet actions. Most were sunk during isolated actions such as the British battleship HMS Prince of Wales being sunk by airplanes on December 10, 1941...or the USS Arizona also sunk by airplanes on December 7, 1941. Any surface actions also resulted in just one or two BBs being sunk. The battleship (battlewagon) had been replaced by the aircraft carrier in WW2.
Carriers fought the decisive fleet actions of WW2. Although there were some "cruiser' decisive fleet actions fought...Java Sea, Savo Island, to name a couple.
yes
Battleship Missouri
The battleship USS Missouri.
Admiral Graf Spee
that someone might have died
Yamato
USS South Dakota BB57
yes
Battleship Missouri
$2000.00
USS Missouri.
See above.
Bismarck.
The four Iowa class.
Tirpitz class.
The battleship USS Missouri.
California built the battleship USS California.