By challenging I meant any asana that after a ‘long’ time of practice (‘long’ being entirely subjective) you have yet to accomplish.
(As to what constitutes ‘accomplished’, I leave that to you, tho I did wish to avoid a tangent discussion as to whether we ever accomplish any asana, as I am one to believe there is always room for improvement).
I avoided naming specifc asanas 1) because I was not seeking instruction on specific asana from this forum, and 2) I did not feel it helpful to say such-and-such asana is easy for me, but such-and-such is difficult(challenging).
What may be difficult for me may certainly be easy for someone else, and vice versa.
We would seem to agree that the process is more important than the goal.
Also, that even a pose such as svasana(corpse) can be considered difficult to do well.
Thank you for your post.
Namaste’