If you can drive (or get driven) to the top, then I’m not sure what the relevance is of “the hard way”. I mean, I could argue that Ohio’s highest point is extremely difficult, if you start at the bottom of Lake Erie, and it’s only easy if you wimp out and start on land.
In that case, the hardest peak to “bag” is Kentucky’s Black Mountain, which is impossible to get to without using the summit road. The land is privately owned by a mining company; the company will let you access the road to the top if you sign a liability waiver, but getting to the peak any other way is trespassing. (I suppose you might be able to hike the summit road itself, if that doesn’t seem too silly.)
I think that might depend on how you define “most people”. I’m 60, not overweight, and in generally good health, although I do have a sedentary lifestyle. A year ago I did a hike with a 1200 foot gain in altitude, on a perfect day, dry with a fresh breeze. It was tough. I did start around midday; if I’d had all day and really paced myself… maybe I could have done 2000 feet… maybe. 3000? Not any more. And it’s not that my legs are bad; I wasn’t even sore the next day. Just not enough energy. (My wife, who is if anything in better health than me but has bad knees, wouldn’t have gotten halfway on the hike I took.)
Damn it, I meant “highest” point. Oh well, they’re probably the same point…
Kansas is flat but not level. The western end of the state is nearly a mile higher than the eastern end.
It also depends on where your starting point is. A 3000’ vertical hike from 1000’ to 4000’ is quite a different story than going from 11,000 to 14000’.