what is the best and the strongest divine object ' sword ' ?? kirito's night sky , eugeo's blue rose, alice 's fragrant olive, fanatio 's heaven piercing , bercouli 's time piercing , Scheta's black lily.
What I found (at the end of Alicization Arc) that Asuna does not know about the special abilities of Radiant and Memories of the Weapon is unknown thus Recollection and Enhancement Arts were never performed. Meanwhile Alice releases her incarnation art Radiant Medium (as I recall) to anhilate the goblin army at once. Bercouli's Time Piercing sword's <<Unseen Slash>> is a rare and restricted art and should be never used (according Bercouli) though he used it against Eugeo once and against the final enemy to slash through time into the past. Kirito's unknown Incarnation Sword Art of the Night Sky Sword absorbed lives of around 30,000 human units at once and later in the, pushing it further the art covers the entire Underworld with it's aura where it absorbs energy from inanimate objects and heals the living ones, and he combines his Starburst Stream with it too. *further info on his sword is full of spoilers
So in the end the Night Sky Sword surpasses any other weapon in the entire Seed Package.