When Ravel wrote Scarbo, he intended that it should be the most difficult
piece in the repertoire.  The trouble is, no on stays king of the hill
forever, and I'm sure someone has outdone him since then.  As to who may
have done that, well, I'll leave the questions to better minds than mine.

Richard, who invites you to visit his music, outdoors and other pages at
http://www.magi.com/~richard/