I meant out of the possible Nightfalls that are available to all at this time. There are certain aspects to Omnigul that make it harder to solo than Undying Mind though. The tight corridors throughout the strike on Omnigul, in particular the last part for Omnigul herself, makes it harder to avoid splash damage than any area on Undying Mind. Especially with Arc burn, going through either entrance to Omnigul to try and attack her gets dangerous when she, 2 other wizards, and Knights with Boomers, are spamming the entrance. I've never soloed Undying, because obviously, you can't unless your fireteam leaves, so I can't make a direct comparison, but I do feel that at least you can use the alley on the left to be completely protected from the boss. You just have to contend with tough ass adds. It's close. I guess we'll see when Xbox gets it and it's a Nightfall.