The Crenshaw Cliffside course at Barton Creek, Austin TX, has some really nice greens with diagonal slopes that resulted from their decision there to in general just use the natural terrain for green sites. The greens are huge, maybe 8000 SF average, and don't have many built up backs. So there are greens that slope front to back, others from left to right, and at least three I can think of that had a diagonal slope.
#3, right front steeply to back left
. This was on a short dogleg left par 4 with a downsloping fairway into an open green. Fun to see your well-planned pitch run all the way from right front to back left no matter what you did! This green reminded me a lot of #10 Oakmont.
#4, front left to back right, pretty gentle compared to #2 but still demanded a careful approach from much farther out on a 410 yard par 4.
#6, 400 yard par 4, very steep slope
left to right. Unpinnable on the left side. Diagonal back left high to right front low, but only about 10 o'clock left rear to 4 o'clock right front.
There were a couple more but you get the picture. The key element was the use of the natural slopes, of which a few were diagonal. This was the most fun set of greens I've seen in quite a while, on an early C&C effort.
Ironically, the Crenshaw Cliffside course is reputed to be the least favored of the four Barton Creek courses. The Fazio I played had generally flattish greens but good looking holes with a couple of exceptions.