Quote Originally Posted by ValiantKnight View Post
Battle speed is one of the biggest concerns.. there are many bosses, especially Z that are just plain HARD if the battle speed is too fast.

Even with a level 75+ party, I imagine you'd have trouble with maximum battle speed on Zeromus.
That's true. However, you won't need a level 75+ party to beat Zeromus with the fastest battle speed. My characters were on levels 64-67 in the Hard Type version of FFIV SNES, and I beat Zeromus without too much trouble with the fastest battle speed.

Quote Originally Posted by Dionysus View Post
From what I can determine looking at the previous posts in this thread, Zeromus doesn't counter Leviathan. Now, if Bahamut was capable of landing 9999 with each MegaFlare, then summoning Leviathan would dish out between 5000-6000 HP with each summon without provoking a counter attack - unless, of course, Zeromus is able to reduce or absorb damage from elemental magic.
I just tried it out, and Zeromus counters Leviathan the same way he counters Bahamut. He first counters with Flare, and later he'll counter by casting Bio on everyone.