I'm looking for some item, or enemy (beside jumbo Cactuar) to gain some Meltdowns.
Where can I get them?

I'm pretty sure you can draw meltdowns from very high level Bombs and Gayla's

Once you gain control of the Garden as a mobile base, head to the snowy Continiant and fight Gayla's. You should be able to draw from them at higher levels plus the item 'Mystery Fluid' that it drops at almost every level can be refined into Meltdowns. This is how I got mine and it doesnt take very long seeig as they'er common items and enemies.

i think meltdowns were all just scattered around,,,, i just forgot the exact locations,, but i believe its not that rare,,

umm.. well i thought so that island closest to hell wouldnt be enough to gain more ultima's,,, but i think you can also get from the place where laguna has a staute,, i forgot the place,, but i believed you have to pay for it.. aw i remember that was just a draw point.. sorry,, but that was the only draw point that can give you as much as 9 ultima's, then youll have to wait the time again..

the sure thing to draw infinite ultima is to Ultima itself,, although it'll take hard work.

no problem is just that i was being lazy and didnt fell like fighting i cant go up any more, thats the problem,whats the point of fighting if u dont level up?

well anyway ive gonttenal the gf atleast

Having Meltdown is pretty easy. You can refine 10 meltdown from a Mystery Fluid (Card Mod a Gayla, win or Mug some from a Gayla, a white monster floating in the air with black stripes in the Trabia area.

You can draw them from bombs when they`ve grown to their largest stage (just before exploding) though its quite tricky.

If i remember correctly they could also be obtained my Status Mag RF. Actually i have at least 300 Meltdowns. In my opinion it's 3rd best magic behind Ultima and Apocolypse