A perfect all-kill happens when a song is #1 on all major real-time and daily charts, as well as iChart's weekly chart. It's a big feat that doesn't happen to everyone (a regular all-kill doesn't include the daily charts or the weekly chart).
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Not only so, but the girls hit MelOn's roof, meaning that their song is charting higher than the standard graph allows.
Congratulations to the girls!
Tip: Krizia Maranan