This type of badge is important, even more so than Unsung Hero and Tenacious.
I just did a totally unscientific survey and looked at a page of 50 unanswered questions that were a couple of weeks old.
Of the 50 questions on the page, 27 had no answers at all - but the remaining 23 had one to three answers.
I would suggest that answers counting towards this (series of) badge(s) would be something like:
The highest scoring answer on a question that has no accepted answers 30 days later
Rather than 30 days, it could be the same interval as the clean-up routine, so that answers are counting towards this badge the first time the question and answer survive an automated clean-up.
A lot of the answers in my survey had no votes at all - but I don't know if that is general, and I think that makes an upvoted answer in this category even more interesting.
Also, a lot of the questions (both with and without answers) were asked by users with less than 100 rep - this badge might make it more attractive to answer even if you suspect that this is a hit'n'run where the OP will never be heard from again.