Hardest Shore climb

^YupX2

Gravel bikes can climb Cypress

Seymour climb could be made easier by climbing Bridal Path, Salamander, Rapid Transit, GSM etc. to cross the powerline at Mushroom, and skip the Powerline puke fest (so same as #2 on the questionnaire, but with a harder start and much more tacked on above Dales) . 

Anyway, I thought the OP wanted "hardest"

Baden Powell Trail. Plenty of sections on there to work on near impossible tech climbing.

I think the BP is like alsmost 50k long, with quite a few large sets of stairs interspersed, so yeah I suppose. Kinda like saying the Triple Crown is the toughest "climb", though...

The BP is just as easily be classified as the hardest downhill