2NE1 - Bad as in not good.
투애니원
Not Bad As In Not Good

Alright, 2NE1. Generally recognized as the most popular KPop group outside South Korea (though f(x) certainly might have more western acclaim). This is the group that a lot people say will be the first Korean artist to take root (as a serious artist, not as a novelty like PSY) in America (or the western world in general).