Diamond Sands from Blast Corps. was a bitch of a level. You have to use the awful Backlash (that stupid dump truck) and destroy buildings on a raised railroad. You can't drive over the railroad, so you have to go under at specific points which takes a lot of time. Failing to do the finicky sideswipe motion with the Backlash and destroying buildings on the first go around almost means an instant reset. Then at the end there's a giant structure where the only means to destroy it are pushing explosive boxes. And it's such a long level too. What a pain.
When I was a kid, I think this was the only level I've played in a video game that made me cry tears in frustration. I managed to beat it, but I'm scarred for sure.