Japan has a few big places to perform, but the Nissan Stadium in Yokohama can field the most number of attendees.
The Nissan Stadium can house 70,000 concert viewers, but in practice it is never held for one day so one has to draw at least 140,000 in order to do a concert.
No female soloist has ever held a concert there, and only Momoiro Clover Z (five times ) ad AKB48 (at its height) held a concert there.
Tokyo Dome had a less tall barrier; with a capacities of around 50,000 (sometimes a little bit less), the following KPop figures had performed concerts there;
Ryu Shiwon (an actor famous during 2000s and popular in Japan at that time)
G-Dragon (by himself)
Excluding Rain and Ryu Shiwon, and counting TVXQ/JYJ/DBSK and Big Bang/G-Dragon as one act,
Ten acts played at Tokyo Dome (plus Music Bank 2011 Tokyo, which was an event and not counted above.)
In Korea, the Gochuk, and the CJ Mnet Arena which has not even built (who knows when it will be completed), house just 20,000 or so so I am not including them.
Only these Kpop acts performed at either the Chamshil Olympic Main Stadium, or the Sang'am Main Soccer Stadium.
Big Bang (Sang'am Soccer Stadium)
One in the Nissan Stadium (plus BTS if the country opens up)
Nine in the Tokyo Dome
One in the Sang'am Soccer stadium (for one day)
Three in the Olympic Main Stadium.
It was easier to fill the Japanese stadium and dome than Korean stadiums!
Plus it is noted that no female soloist in Japanese history tried a concert at the Nissan Stadium.
In Korea, a certain soloist tried to hold a concert at the Olympic Stadium. She is not included above because she is NOT a KPop singer (although her recent song might finally qualify her as one), but considering no Japanese female soloist ever held a concert at its largest venue, the nerve of the certain soloist to hold a concert at there would have put her ahead of all Japanese female soloists and in the same league with BigBang, EXO and BTS.