Board Thread:Naruto Discussions/@comment-27662856-20180316054643/@comment-9782468-20180319150204

Ace Chouno wrote: I want to clarify too that the Sharingan being able to copy any jutsu was not seen. I do not know if it was stated but even Kakashi, Itachi and Sasuke never copied a jutsu that was above B rank. Kakashi has stated that at the level of the Rasengan, he would just be able to copy it. So A-Rank is probably the limit.

Copying is really just dependent on the capabilities of the user. If the user has the skill and chakra to perform the technique, they can copy it. So Kakashi could probably copy S-rank techniques of Lightning, A-rank of Water and Earth, and lower level techniques of Fire and Wind (he has no feats in those departments besides anime and databooks).