I can't possibly remember enough rides to rate and rank them against each other. A couple of summers ago, I did a solo century ride which was actually 96 miles. I had various challenges.

I didn't want to use turn-by-turn navigation, so I made a route with google maps the night before. But I didn't have a printer, so I wrote them out by hand. I lost one of my cue sheets, so I did use turn by turn for a few periods necessitated also by getting lost.

My rear derailleur (9 speeds) failed so I jury rigged it into a middle cog and had a three speed bike after about mile 35. Then I hit a big hill called Hosner Mountain (in Duchess County, NY). I made it up without stopping. It involved pedalling really slowly, and I think balance was my savior, not strength. It was almost like track standing.

I wasn't in proper shape, so the toll on my back and shoulders was tough. By the time I got to my destination, it was hard to pedal, and after getting off the bike, it was hard to walk or do anything. But I made it. Now I'm doing a lot of exercise, building up my upper body and getting more limber. I'm also doing more miles per year. I expect to do a lot better this year.