1) Character/Class Tiers: F -> E -> D -> C -> B -> A -> S -> SS -> SSS -> EX -> X -> XX -> XXX -> Z -> ZZ -> ZZZ.
Each tier has subgrades as well (e.g., C-, C, C+).
2) Items Tiers: Common -> Uncommon -> Rare -> Epic -> Legendary -> Mythic -> Divine -> Arcane -> Ether -> Eldritch
3) Skills Tiers: Same as character, except it stops at SSS for awakening. Another complete section for how strong the user makes the power, which can go up till ZZZ.
4) Creature/Beast Tiers: Same as characters, all the way to ZZZ
5) Dungeon/World Threat Tiers: Same as character, all the way to ZZZ.
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I should specify that for any normal mortals, doesn't matter what type of mortal (e.g., humans, goblins, and more) the skills stop at SSS, but mortals can always push further and go beyond.