who is the biggest rookie kpop group ever?

7 months old Blackpink charting on under hot 100 while had about 1 min on boxbluster Hollywood movie

Seo Taiji and Boys. Their debut song "난 알아요 (Nan Arayo)" is credited for establishing K-pop as we know it today, so yes, you could say that K-pop started with them.

2Ne1, Winner, iKon and BP all had crazy successful debuts. Massive debuts were YG’s thing back then.

Twice released two national hits in just over a year after debut. It doesn’t get better than that.

When it comes to physical sales Wanna One is pretty unbeatable. They flew high and fast.

yeah probably