Seems Gaon data is pretty straightforward
Artist with most number one songs
IU > Big Bang > 2NE1, Sistar, Twice > Huh Gak, Girls' Generation, Davichi, BTS > Zion.T, Taeyeon, Park Hyo-shin
Artist with most weeks at number one
IU > BTS > Big Bang > Twice > Sistar
Artist with most months at number one
IU > Big Bang > Davichi, 2NE1, Psy, BTS > Girls' Generation, Blackpink, Wonder Girls, G-Dragon
I don't see Epik High, BTOB, BOL4 etc.
Twice is far more a Digimon than Blackpink is, understandable given their lack of discography, too many singles.
But sure this can be improved upon, if someone is interested, with some criteria like
At least 3 consecutive releases of Albums/EPs with more at least 4 songs, with
- At least one song in top #5 on Gaon Digital for Topping
- At least one song in top #100 for 50 weeks for Longevity
- All songs hitting within top #25 at least once for B-sides
If an act has 3 such release, then they can be considered a Digimon for that period.
That would trim the above list some more. Everyone else is simply not a Digimon.