The same way you killed the Tonberrys? He is harder then the normal Tonberrys but not by THAT much...or at least I didn't think so...
If that fails, which obviously it has, then try this:
If you thought the Tonberrys were difficult, you're not going to want to |
| face off against this guy, that's for sure. Not only is the Tonberry |
| King's HP total through the roof, his attack powereasily matches it. |
| Tonberry King's normal attack will really hurt you, but the big damage |
| comes from the Junk attack where all sorts of crap just falls down on |
| your head. Both of these attacks can be reduced in damage if you have |
| your party under the Protect status. Most of your support doesn't |
| actually have to come out of your magic inventory since the Tonberry King |
| is filled to the brim with helpful spells like Full-Life if you need to |
| use them, maybe if you're strong enough you can even try to stock up |
| on them too! When it comes to damaging the Tonberry King things get |
| difficult. Obviously the Kamikaze method isn't as helpful since it isn't |
| a one hit kill and you just lose the character, perhaps when you know the |
| king is getting close to death you might want to use it provided you don't |
| mind that character not getting any AP. Gravity too, is ineffective here. |
| The Tonberry King is immune to it. Damage will have to come in the form |
| of powerful Guardian Forces, physical attacks, or my personal favourite, |
| limit breaks. By this point in the game you should have access to at |
| least some Aura magic which makes it so your characters can use their |
| limit breaks even if they have 9999 HP. If you do not have Aura magic |
| then you'll have to either try to stick through the fight with a low |
| HP total or go back to Guardian Forces and physical attacks like I said.
Taken from here:
http://www.gamefaqs.com/console/psx/file/197343/37211