Wikpedia has more info, plus WNN and other industry publications usually are more up-to date.

Kori[1] has 7 operational units today and 1 commissioning and 1 under construction

Hansul[2] has 8 operational units and another 2 more under construction.

All 4 new units are APR-1400 reactors ~1400 MW capacity. Kori should retains its top position, Saeul-3 in Kori Phase II has already reached criticality in April.

Tianwan in China will come close but its 7/8 units are slightly behind in construction than Saeul-3/4 in South Korea, plus the plant is also bit smaller at 6600MW now . The Russian VVER-1200 design China are using is also slightly smaller than Korean APR-1400.

[1] https://en.wikipedia.org/wiki/Kori_Nuclear_Power_Plant

[2] https://en.wikipedia.org/wiki/Hanul_Nuclear_Power_Plant