The "Championship Races 2023" thread has drifted into a discussion on what is the best short race. So to keep that one on topic, here's a new thread.
So far we have had Callow and Dunnerdale suggested. I would offer Scafell Pike: and not just because it is the last race I ran. It is even steeper than Callow: 900m of climbing and descent in 7.2km. Of course, if steepness is the only criterion, there is the Wasdale Head Show race up Kirkfell: more than 700m vertical in under 4km horizontal.