Ymir is built for creating things, and he indeed created a primal beast capable of defeating the Original Thor. That alone makes him special. Surtr seems notable.
We already saw how Europa was capable of actually dealing with all of them alone until they used Branch hax. Which already shows they are not really on their level (Disciples). (Although we can argue this is Europa FLB where she's already stronger than a Primarch with Galilei's Insight hax that stems from miracles/Reality warping)
Violet Knight from the Ruined Sky-realm has the King's eye, which makes him far superior to the one who died in the main timeline.
Green Knight fought mostly in the sidelines as she is more of a secretary
White Knight definitely should be far stronger than Crimson Knight.
The Golden Knight and the Black Knight are equal
With Crimson Knight probably being slightly above them in strength, since it did say Scarlet Knight is known for his strength even among the Luminaries
Blue Knight is the direct scaling for Eternals, but IIRC the eternal event should have happened way later when they are all already 4-A.
6-A is reserved for Tiamat and early primals
5-A is for War primal beast like Corow
4-C is reserved for certain primals as their maximum limit, like Malice scaling from Eternals and Luminary Knights, as Even Black Knight struggled to fully subdue Malice Yggy
Vyrn restricted Akasha hence I'm not sure about letting people fully scale from Akasha's 4-A rating.
What we can use though is Echidna since iirc she took care of even war primal beast and Gilbert being granted authority and power by True King which might make the character at that point 4-A specially with innermost teaching
but that means
Zeyen should also be 4-A with innermost teaching. It would make sense though since Innermost teaching let them beat Scarlet Knight who is known for his strength among Knights