S-rank
From Narutopedia
S-rank is one of the six classifications. It is preceded by A-Rank. It is typically used when classifying jutsu intended for highly experienced Jōnin and Kage-level shinobi. S-rank jutsu are almost always unique to a single user, and as such are trademark abilities of that user.
There are also S-rank missions, the highest paying and most dangerous type of mission a ninja can go on. These missions are exclusively assigned to highly skilled Jōnin or large squads of ninja. S-rank missions pay at least 1,000,000 ryō.
"S-Class" is also a designation given to extremely powerful missing-nin, earning them a place in their village of origin's Bingo Book. Each member of Akatsuki is an S-Class criminal. Fans of the series will sometimes classify powerful ninja who are still loyal to their village as S-Class, such as the Sannin or other Kage-level characters, but this is arbitrary.
