I love climbing, but my shoulder is fubared and I struggle up the really steep hills with the gears I have - 39 x 24 is the lowest my best bike takes.
The only hill I haven't got up (without stopping) due to my shoulder was the Jenkins Chapel ascent of Pyms Chair - just outside Macclesfield in the Peak District. This is upto 1 in 5 but the gradient constantly changes, it's quite long and it's twisty - you can't see the top, so its psychologically hard too.
I will get over it one day, but I try and avoid going that way as you've got a choice of Pyms Chair or Lamaload (which is a pig but it's a constant gradient of 1 in 5)
South Wales has so many steep and long hills, that it's too difficult to choose just one of them! There are a couple on the Dragon Sportive, that will test some people, but here's three of the almost vertical ascents in our area > The Glyn! The Sugar Loaf! Bleanavon from Abergavenny! And there are lots more of them in this locality, we cannot avoid them, we are surrounded by them.
Ive been talking to Marinyork amongst others about Peak climbs. Ive cycled all over the peaks without knowing their names ( Only realised where winnats was the other day) Have you got a link to that climb ?