Last known photo of the Bismarck while still afloat; May 27th, 1941.
KM Bismarck was the name ship of the largest warship class Germany produced in World War Two (although her sister Tirpitz was slightly larger once completed). He faced two enemy capital ships in battle with only a heavy cruiser for support. He destroyed HMS Hood in that battle (the pride of the Royal Navy for a couple decades) and damaged the battleship Prince of Wales as well. You can read a detailed account of the battle here.
He was a fast ship (about 30 knots at maximum speed, but with a sustained speed of about 20 knots for long range cruising) and powerful enough to threaten any convoys encountered. Unless the convoy was escorted by an old battleship, Bismarck would have forced the convoy to scatter so that some of its ships would escape. (The minimum sustained speed a merchant ship needed to make to be allowed in a fast convoy was 10 knots, otherwise it was restricted to the slow convoys of 8 knots, though in practice the convoys averaged speeds of 0.5-1.0 knots slower than this.) Simulating battles of Bismarck vs another solitary battleship in defending a convoy is a favorite of wargame enthusiasts and much detailed information in comparing the ships is available.
Bismarck’s rudder was jammed by a torpedo launched by a biplane from an aircraft carrier (the critical hit of several scored). This jam was not repairable at sea (going so far as to blow off the rudder with explosives was considered) and doomed the ship. Bismarck again faced two capital ships, and King George V and Rodney scored hundreds of hits while taking none in return, leaving Bismarck in thoroughly ruined condition. Some like to play guessing games as to whether Bismarck sank due to enemy shell fire or due to scuttling by his crew, but this is an artificial argument over semantics.
There has been some detailed analysis (and much under-informed debate) of why HMS Hood exploded after a handful of hits, but Bismarck didn’t after hundreds. The short answer is that battleship caliber shells designed before and soon after World War One were incapable of penetrating heavy armor and then exploding inside their targets. This meant that capital ships of that era (Hood, Rodney, Kirishima, and others) were designed and built to take heavy exploding shells on their outer surfaces. Technology had improved by the time the battleship holiday had finished so that the shells designed and used in World War Two were capable (at least under some conditions see immunity zone) of piercing heavy armor and detonating inside. This produces hugely more damage and could send fragments into critical areas of the ship (the magazines and engine spaces). For this reason, ships designed after the battleship holiday also included thinner armor inside the ship, to keep these fragments from reaching the critical areas. This meant that a new battleship fighting an older one had a large hidden advantage (the new ship could survive hits that would much more easily cripple or kill the old one).
These are only some of the reasons Bismarck is a significant ship. There are other aspects: the underdog fighting the entire enemy navy, the “lucky hits” on Hood and torpedo on Bismarck, the potential “what ifs” (Bismarck is not hit in the rudder (actually dual rudders) and makes port in occupied France or faces a single BB in attacking a convoy), as well as the relatively few members of her crew to survive (though Hood only had three survivors).