If Dreadnought Ω is fought on later days and on hard mode, it can have HP values of up to 5 million. Its Flame Cyclone attack can kill Lightning in a combo even while guarding, and its Pulverize is equally deadly.
The easiest way to take it down is to keep distance and use Blizzard attacks. Eventually both its arms will break off, and then it's a matter of hammering it with ice attacks until it staggers and then going in for the kill. The Flame Cyclone attack can still hit at a distance, but equipping a Fireseal Jewel or Flamebane Choker will make it easy enough to heal through with Mediguard. The most important part of the fight is keeping distance to limit the attacks the Dreadnought can use. Once its arms are gone, it mainly uses Wrecking Ball. Even with a battle time of 5 minutes 5 Stars is obtainable.
[view·edit·purge]Dreadnoughts were a type of battleship popular in the first half of the 20th century before the advent of the aircraft carrier made them obsolete. They were gigantic heavily armored ships noted for an "all-big-gun" design that allowed for great firing range while being well-protected. The term "dreadnought" comes from the first major ship of this design, the 1906 HMS Dreadnought. The word means "fear nothing".