I'd imagine that the hardest pitches--at altitude-- here in the Wasatch would most certainly be found at Lone Peak Cirque. There may be more difficult moves on certain sport lines in the Uintas, for sure, but the steeper lines on the Question Mark Wall, for instance, combine sustained climbing, tricky gear and an approach, to boot. I'd have to say that the Question Mark Wall Route (5.12b/c, 3 pitches, FFA: M. Bitter, S. Ruckman, 1989) and, perhaps, Rare Form (5.12c, FFA: J. Knight, S. Sanders, 2002) would give you a run for your money; they'd no doubt be the most challenging to onsight, as they're traditionally protected and feature far less chalk on the holds than a popular, hard sport route. Giv'r!!!