Here is the list, not including vessels of the same class, of the greatest Dreadnoughts ever to sail the seas:
1). Japanese Yamato-72,809 tons
2). American New Jersey-55,710 tons
Likely the most famous version of the 4 Iowa class, this was the largest American dreadnought ever constructed and also the fastest. At 33 knots she could keep pace with the new aircraft carriers that now dominated warfare at sea.
3). Germany's Bismarck-50,153 tons
The most feared Nazi surface ship of World War 2, she had a short life span from her monumental sinking of the HMS Hood in May of 1941, to her own demise just 3 days later.
4). French Richelieu-47,500 tonsThis unique design also holds the singular record of fighting for both the Axis and the Allies. While in service with the Vichy government, she fought duels with British and American battleships, when she was only partly operational. After the French rejoined the allies after Operation Torch, Richelieu served with the British Fleet in the Far East.
5). British Hood-46,200 tons
Technically a thinly armored battle cruiser, Hood was never used in this capacity but as a front line dreadnought. This error in judgment by the Royal Navy eventually led to her destruction when she met the battleship Bismarck. Yet, between the wars she was universally renowned as the mightiest warship afloat!
The most heavily armed battleship for her size was the HMS Agincourt of the Great War. This 30,000 ton titan carried a total of 14x12 inch cannon in an amazing 7 gun turrets!