Zeromus - Big Bang is just too powerful. And Leviathan would face some nasty magic counterattacks when he casts Ice 2 on Zeromus.

Ogopogo - Wow, would this be a close fight. The only problem is Golbez is a sorcerer, and can only cast magic. Ogopogo has nasty magic counterattacks when inflicted with any magic damage.

Wyvern - Bahamut wouldn't inflict any damage, as his MegaFlare would be reflected back onto him. Bahamut should beg for mercy from his evil twin brother.

Evil Wall - Odin's sword can slice many creatures into two, but not a gigantic, thick wall.

Plague - Count is a very cheap attack. Pale Dim could not inflict enough damage in 10 seconds.

Rubicant - Unlike the other elements, Rubicant is intelligent and would quickly find the strategy to defeat the CPU. I do not believe his scorch attack can be reflected.