Would this be a one-time purchase or all games, or would unlocking it work until you died?

It's not necessarily irrelevant. Why not keep track of the kills in the Quick Game mode? Or better yet, just count the kills *and* goals in ranked mode. At any rate, I liked the edition of the "per capita" so we could see which countries were doing best. It was like an Olympics of sort. Now it's just tracking the exact number so the countries with the most players always have the most goals.