How did South Korea unify the world during the Warring States Period?

Basically impossible, for the following reasons:

First, as one of the Seven Heroes of the Warring States, the other six countries sometimes dominated, such as Wei when Wuqi and Pang Juan were in power. Zhao Wuling, Zhao Wang; Qi State where Sun Bin and Tian Ji are located; Yan State when Le Yi was a general; Wu Qi went to Chu after Chu. It's just that South Korea's national strength has been relatively weak, and it has not been able to dominate for a while.

Second, South Korea has mountainous terrain, less cultivated land and insufficient grain and grass.

Third, in fact, there were only three countries that really dominated the country during the Warring States period. After Shang Yang's political reform, Qin had the strongest military strength, and Qi was located in Shandong, surrounded by the sea on three sides, with the best terrain. Chu has the largest territory. In other countries, Zhao, Wei and South Korea are separated from Jin, while South Korea is between Qin, Zhao, Wei and Chu, and the terrain is quite bad.

South Korea wants to unify the whole country, unless it can unify Jin, that is, destroy Wei and Zhao, and then conquer Yan, it will have the strength to compete with Qin, Chu and Qi. But in fact, due to the congenital defects and geographical location of South Korea, this is basically impossible. Not to mention that South Korea's national strength is the weakest, even if South Korea becomes stronger, other countries will not sit idly by and watch it annex a big country.