True "mountain golf" is hard:
Cordillera Mountain Course (A Hale Irwin Design!) Yes, I would play again to try to avenge my first play, but I live very close by.
Red Sky Ranch Norman Course. Would play again. Front 9 from the tips is a 152 slope, back 9 is much easier. First 4 holes not a gentle handshake but a swift kick to the nuts. F9 closes with a 559 yard PAR 4 (tips)!
Others:
The Bear, Grand Traverse Resort. I was about a 15 when I played here, now I'm a 3, so not sure if I'd like it better now. Instincts say I would not play again, especially if I could get on some of the other tremendous TC courses.
George Dunne National, Chicago area. Brutal. Would not play again.