Most difficult levels in existence?

[AdrenalinDragon]

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?).

From what I remember as well, some levels that were originally voted in CCLP2 didn't get in because the staff couldn't get hold of their original creators, but I might be wrong.