What bosses have GFs that must be drawn out in Final Fantasy 8?

Answer 1

Siren drawn from  Elvoret (disc 1)

Carbuncle drawn from Iguions (disc 1)

Leviathan drawn from NORG (disc 2)

Pandemona drawn from Fujin (disc 2)

Alexander drawn from Edea (disc 2)

Eden drawn from Ultima Weapon (disc 4)

Those are all the ones that need to be drawn out. Hope that helps!

Answer 2

Siren from  Elvoret
Carbuncle from Iguion
Leviathan from NORG
Pandemona from Fujin
Alexander from Edea
Eden from Ultima Weapon

In case you forgot to Draw these out of each boss, you can draw them out of the bosses in Ultimecias castle, right when you are defeating them in order to get you abilities back, this works great in case youre having troubles defeating Ultima to get Eden.