so theres the obvious Bahamut/Shiva/Ifrit
and I think theres a tier of Ramuh, Leviathan, Titan as the other recurring elemental guys who took a pretty long break. (and maybe youd give the nod to Ramuh on the basis of Thunder being a more consistently prominent element than water and earth) Not being in X or XIII holds them back a bit.
but maybe you could sneak in Odin between the S tier and the A tier, because hes more distinctive than just being one of the elemental guys, hes generally cool and powerful, and hes tied to the main character of one of the games
For your
Azuarc
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At least Kupo has class and doesn't MESSAGE the people
-Dr Pizza