rasgoat wrote:Without a doubt, Kaaterskill High Peak from Palenville... 2950 feet of gain
I did that hike last summer and it was a lot of fun, but the gain is spread over like 6.5 miles each way for a 13-mile RT. Basically anything that starts at the BOTTOM of the Wall of Manitou (look it up

) on the east side is going to have a bunch of gain. Blackhead starting at the Dutcher Notch trailhead also has like 3K gain and a bunch of mileage - might do that one this summer. I remember doing a winter hike of Wittenberg from Woodland Valley that also had around 2,500 to 3K total (EDIT - oops, already mentioned in the OP).
As for steepness, it's all over the place in the Catskills but is seldom sustained for more than 1,500 - 2,000 feet.
Cheers.