The best weapon you can have is the Yagyu Darkblade you get from a rare drop from a rare fiend in the Lhusu Mines. I'll post a link to a youtube vid: YouTube - Final Fantasy XII - How to get Yagyu Darkblade Apart from this, the best possible set up is beserked, hasted, bubbled Masamune-weilding characters (Basch and Balthier were my favs) -VS- Masamune-weilding characters that take advantage of the Infuse Technick...basically leaving them with ~ 10 HP will make their katanas combo MUCH more often. At the beginning of the battle, use Expose several times to maximize the amount of damage done to him (9999, 6999 later.) Using Shellga on your party is also a good idea when Yazy is spamming his instant death attack as it will make him miss 1/2 the time.

I'd say that your lvl 70ish characters would be a good choice...followed by a backup party in the 50s or 60s or higher. Keep in mind that you don't have to do all his 50million + HP in one sitting, you can run to and from the save point to restore you HP/MP and fallen party members if needed. Just don't stand around reviving everyone where he can't hit you because he'll cast Renew and all your hard work will be for naught.

Gambits towards the end become less important. Keep bubble up at all times unless you chose to use Lure + Reverse on your magick user...although I would say that if Reverse falls you'd best have bubble on anyway. = P The first time I fought him it took me about 6 hours...the second - 4 1/2. I was much better prepared though....and there's vids on YouTube that show you can do it in under an hour!

That's all really. If you have a party with the Tournesol, the Zodiac Spear and a Masamune...you should do fine. The last few bars seems to take forever - just remember to dispell Reflectga when he casts it on your party and Dispel HIM each time you enter the screen. Reviving your fallen party members during battle takes priority over ALL other actions here... and adjust your gambits accordingly as he's becomming more and more difficult. In the end... I basically only attacked once all my members were under Protect, Shell and MAYBE Haste...and I had Bubble Belts on everyone.

I truely hope this helps people who take the time to read it. D: