Sometimes it's the short ones that get you:

Just a quick morning ride before work. Two miles out and I flat. Fix it and flat again (forgot to check the tire!) Fix it (patch this time) and flat again. At this point I give up and decide to walk home. Not easy in road shoes, not safe without them. Now it starts raining. Where did that come from? I decide to take the most direct route home and cut through the industrial parking lot. This ends at a 6 foot high chain link fence that goes on forever. I can see my house ahead and that spurs me to climb the fence. I take my shoes off and climb up. I reach down for my bike and raise it over the fence. I climb higher and lower my bike safely to the ground. I climb over and reach the ground safely. I go to put my shoes on and... Back over the fence. It's still raining. I throw my shoes over the fence and climb back over. My new shorts get caught and rip, now showing off my wet rear end. I get home, walk into my house, and my wife, without looking says, "that was a quick ride!"

I must be lucky.
I don't have just one worst ride, but a collection of rides each with bad elements.

Two years ago in England: It rained for 2 weeks, 135mm of the wet stuff. I was heading for Faversham from Canterbury. I was between OS maps and being VERY Canadian didn't want to buy a chart I'd only use for 12 kilometres. I got lost, took directions from a farmer who sent me up to the M highway. At last I found a marked footpath. Did I mention it was raining? The footpath took me no where and within an hour I was on a muddy trail in the middle of an illegal pheasant farm. I don't actually know that the farm was illegal, but it looked like it was. With signs all around reading "No cyclists allowed with guns", I weighed my options.
I was completely lost in a foreign country. It had been raining for two weeks and I was miles away from civilization along a muddy trail with a pheasant trying to land on my helmet.

Last year in Ontario: I'd biked from Windsor along the Chysler Trail and the Trans Canada Trail. The map showed a rail trail from Simcoe to Brantford. It did not exist so I was forced to bike on the shoulder of a major road with fast moving SUVs owned by people who disliked bicyclists. I discovered that if I went east one sideroad then north one sideroad I could avoid the heavy traffic half the time. Problem was, I was heading too far east to get around the Grand River. When I finally got to the Grand River there was a huge westerly and I had to bike right into it, for 12 kms, something I had tried to avoid by travelling west to east. When I finally got to Brantford and hit the trail trail, I found I was lucky. I was going downhill to Hamilton. It was sunny and I was down to shorts and top. Against the wind, at least 40 km/hr and going uphill was everyone else. They thought it was hot when they started, so they only wore their t-shirts--getting back was uphill into the wind and not t-shirt weather.

Go with God