You should see some of the Ontario high school courses. The past two OFSAA championships have been hosted on (a) a cross country ski course that is hill after hill, mostly up before finishing with a massive downhill, and (b) relatively flat with some undulations until near the end where there is an 150/200m hill straight up (very high grade). Senior and junior boys must run this hill twice. Many very strong runners have walked up part of it.
If you want some tougher courses, this would be one example.