Although it does contain some pioneering ideas, one would hardly characterize the work as __________.
Here the word although defends the fact that the ideas are pioneering, but hardly negates that and suggests the opposite.
Thus although (in the sense of even though) the work contains pioneering ideas, and thus one would be expected to characterize it as pioneering, hardly one can do so.
The correct answer choices are original and innovative.
Here the word hardly = almost not. As in, I hardly work, meaning, I almost don't work.
although = emphasizer
hardly = negator
OR
Although it does contain some pioneering ideas, one would call the work un-original.
Although it does contain some pioneering ideas, one would hardly(not) call the work original. (the "hardly", meaning "not", cancels the "un" in unoriginal giving us original).