Board Thread:General Discussion/@comment-73.252.180.8-20160622131217/@comment-25047329-20160622222521

Ratings are more to signify rough danger level rather than strength or battle prowess more than anything. There are criteria to designate ratings and it relies on opinion and knowledge of said ghoul. Currently, it's unknown what criteria a ghoul must fulfill to be designated a SSS.

As far as Kaneki or any other ghoul goes, I don't think they'll invent a higher rating. SSS is the definitive "you're fucked" rating. Some SSS ghouls might fuck you up more than others, but by that stage, the CCG understands that when you encounter a ghoul of that level you just throw everything you've got at them and take the upmost precaution.