The Sportsmanship badge description states:
Up voted 100 answers on questions where an answer of yours has a positive score.
Just curious, but why does it require a positive score?
The requirements for certain badges are set such that it's more difficult to "game" your way to earning them.
Imagine a scenario where someone hunts down questions that have a lot of answers, drops off a marginal reply on each one, and then proceeds to upvote all of the competing answers. This user would be only limited by the number of votes allotted to a user in a given day, and could get the badge in about 3 days or so.
So, with the stipulation that the answers be quality ones, the badge requires a positive score (upvotes - downvotes) on a given answer for it to qualify.