Leviathan. He was the first "Hard Mode" Primal that you pretty much had to TRY to wipe, in order to wipe. I was so disappointed at how easy he was; I think the only Primal easier was lvl 20 Ifrit. Hard Modes for Ramuh and Shiva were almost as easy (Mog, at least, took out a few of the early, unskilled parties I ran with).

Additionally, Leviathan was the first Primal to bring MINIONS into the fray. I was so disappointed to see Sahagin on deck. It was like, "Is Leviathan so insecure he has to call for reinforcements? Do the Sahagin have so little faith in their god they think he needs help?" Bismarck was even worse - though, oddly, I didn't really feel bad about it at the time. Maybe because Leviathan had softened me to the notion, or maybe because Bismarck had some interesting mechanics.

Anyway, Levi gets my thumbs down. I didn't even like his music.