Most difficult levels in existence?

[jblewis]

No offense to anyone whose levels feature significantly in CCLP2, but that set just smacks of a kid who's just acquired a great new toy but doesn't know just what to do with it. Like a child who sits down at a piano for the first time and just starts banging on the keys. It's a lot of fun for that person, but also pretty annoying for anyone within earshot.

Completely agree. I don't think CCLP2 was comprised entirely of these sorts of levels, but I feel like the narrow pool of submissions allowed them to get in, and many of them were created in the period when submitting custom sets was just starting to become popular around the community. Invalid tiles, random force floors, and the like - although not bad things inherently - were used in ways that, in hindsight, probably weren't quite the best ("Keep Trying," anyone?).