Abyssion weapons: 1-hit kills!
This is quite good if you want a very powerful weapon, better than the best ones in the game! I'm going to this from Lloyd's perspective.
So, get the weapons and defeat Abyssion. If you're on a high difficulty, turn down to normal at this point. Now, goto earlier points in the game and equip the weapon that you had to get for Lloyd for the quest. Kill a ton of enemies, and I mean about 100-200 enemies so it gets stronger. Do this on stronger and stronger enemies, and eventually (About 3 hours) it will be better than the tasunagi blade. If you do it long enough, you'll be able to 1-hit most enemies (except bosses, take a few years of killing enemies for 1-hitting them). If you want a dynamic ending to a battle, use this with rising Phoenix or something similar.