Oh man id go with a good raw hammer. But i heard that weapon can beat him if you use bombs as he comes in the areas and anit dragon.

i've never tryed useing a long sword.  but a good strong hammer to his belly will do the trick, or duel swords to his belly or his back right leg to trip him.  But my favorite weapon for him is the Bow with armor that gives you adrenaline 2 or get feline heroics.  With the Bow and some bomb you can brake his face easyly, and you can also attack him even before he enters the area.  You can also brake both his shoulder's with the bow. remebmer the more stuff you brake the better reward's you get. There are youtube video's you can watch that will show you how to use the bow,duel sword, and hammer.  with any luck you can find one that show how to use the longsword.  Good Luck and Happy Hunting

Probably the Eternal Annihilator or the True Dragons Jaw... I like that sword.  Raw power for the Greatsword is more important than the element.