You can start on the slam quest. All kinds of attainable critters are on that list.
It is the ones that require a guide, the ones that require a lot of either luck or time just to meet up with the critter, that make this list tough.
Then, there are the critters that can and will knock you upside down if you piss them off. Can you crawl 20 yards or less from a brown bear and shoot it well ? Not everybody can.
In order to do this, you need money and you need to be driven. Not everybody has enough of either to even try.
What I wonder. . . how many of those that did it, or are very close, did it just to experience the hunt, or was there some other, ulterior motive driving them ( like being first, or the royalties possible for having done such a thing).
ChuckC