I've mentioned this before on here, but at the Realp club, high up in the Gotthard region of Switzerland, the tee boards have, as well as the hole length, its elevation change on them.
I can't remember them all, but the third hole is a 284 metre par four that rises more than 50m (165 feet)!
That's the steepest I've ever seen.
Steepest in the UK is the first two holes at New Galloway in the Scottish borders. The course starts in the valley and heads straight up onto the hilltop -- the first is a brutal 216 yard par three (for men, it's a four for women: best to be a woman), and the second a 252 yard par four, both really severe climbs. Then you emerge onto the moor, and it's a really lovely course from then on!