A shelter you can pitch and strike alone, in wind, in the dark. That single standard removes half the catalogue and most of the regret.
The group normally shares these jobs. Alone, they are the trip's insurance policy, and the only group on this list that grows with remoteness.
Cooking alone succeeds on repetition, not ambition. Simple hot food, counted water, and smells sealed against animals who know you are the only one on site.
Nobody tags you in when the UV peaks or the storm lands. The weather group is self-rescue equipment when you camp alone.
The solo trip is bought for the intangibles. These lines are why one-person trips get repeated rather than survived.