The next closest BG is BTS with 4. 2AM has 3. Everyone else has 2, 1, or zero.
Melon Weekly is the toughest chart in all of Korea. You're going against literally everyone in the Korean music industry, including famous balladeers, trot singers, and viral acts from whatever genre. And mass fandom downloads cant bail you out, this aint Gaon lol, you need REAL UNIQUE LISTENERS.
I'm telling you, Bigbang was bigger than IU. IU might have more #1 songs on Melon Weekly at this point (she's probably around 18-20) but that's because BB was cut short due to military and then Burning Sun. If they were left uninterrupted, BB would probably have 25 #1 songs by this point.
This is why i have always stated that Bigbang is the biggest musical act in modern Korean history (since the advent of digital music).