Final Fantasy VIII/RPG Maker

[Ultima Shadow]

His basic stats are all 255 in the original game... so keep that.
Add immume to all Stats-Effect, including Meltdown.
Make it 40,000,000 HP

Actually, no. They are not all 255. These are Ultima Weapons stats at level 100 in FFVIII:

HP: 160,000
Str: 254
Vit: 188
Mag: 213
Spr: 160
Spd: 145
Eva: 5

And yes, Meltdown should also be included.

Make it 40,000,000 HP
Add: Auto-Shell, Ribbon
Add:
-Pulsewave Shocker (the only attack that deals over 10,000HP-40,000HP. Used by Griever and Quistis)
-Meltdown
-Meteor
-Lionheart? You would know one character's dead if not invincible.
-Add Powerga, triple his magic/strengh.
-Add Salvation, remove all invincibility, must use Ultima or Meteor just after.

40,000,000 would actually be a little too much. I'd prefere a battle that would take around 2 hours. With 40,000,000 HP the battle would probably last atleast 4-5 hours. And that's just a little too much.

I actually don't want Auto-Shell. Auto-Protect and 255 vit (and immunity to meltdown) is there because it would discourage the use of physical limmitbreaks such as Lion Heart and Armageddon Fists(which are the most powerful limmit-breaks, save The End), and encourage the use of Magic-based Limmit Breaks instead, which could make things a bit more interesting. That's also why Ultima Weapon's spr shouldn't be max'd.

Also, what does Ribbon do?

Interesting move-suggestions, though. Something that removes invincibility would certainly be welcome. Lion Heart wouldn't quite fit, though. Maybe "Weapon Heart"? xD But nah, I think Light Pillar does the job at finishing a character off good enough. Salvation should also dispel other positive effects such as Aura, Haste etc.

With auto-haste and 255 speed, you don't have any idea how insanly fast he will be.

Well... he, alone, is supposed to be just as fast as your entire fully junctioned and hasted party. Something no boss or enemy in FFVIII actually is.