he would go alone to the quarry, collect a load of broken stone and drag it down to the site of the windmill unassisted. (source: Orwell, George. Animal Farm (p. 43). Sanage Publishing House.)
I just can't understand why the word "unassisted" is used. In my opinion, there should be an adverb instead of an adjective to modify the verb 'drag'. So I search the dictionary, and I find another case.
He has made a good recovery and is now able to walk unassisted.
Finally, I think it's something about the linking verb. I'm not quite sure.