S-Rankings is a group of ranks given to some of the most powerful ninja in existence while having their own category. Ninja's with these ranks are noted as very dangerous and normally have a price of over $8,000,000 Ryo for them.
These are basic S-Ranking ninja. They are given to a basic powerful being and are normally around $5-$8,000,000 for pay. They are still powerful and shouldn't be messed with.
These are given to very powerful beings like Tailed Beasts and Kage. They are viewed as dangerous beings and have been given the price of around $20,000,000 Ryo for alive or dead.
The strongest class that anyone can obtain without Senjutsu, Sage of Six Paths Chakra, etc. They are viewed as the most powerful ninja in the world and are extremely dangerous in many cases. Kage and Tailed Beast easily fear them and their chakra is enough to block out an entire village. They are asked for around $40,000,000 Ryo.
Known as unearthly, the most powerful rank in existence. Given to only unearthly beings, beings that are either in full control of Ten-Tails, possesses the Rinne-Sharingan or even has an enormous god-like power in their position. They are extremely dangerous and people view them as power godlings. They are asked for over $100,000,000 Ryo.