Which is the largest country in Asia?

If you want a country that is entirely in Asia, than it's China.

Russia which occupies 13 million sq KM of Asia.

Bhigistan...............

The Russian Federation, simply often called Russia, is the world's largest country by area. Although Russia lies in both Europe and Asia, i.e. Eurasia, by far the greater part is in Asia. Russia is the largest country in Asia. The largest country, by area, entirely within Asia is [the People's Democratic Republic of] (a.k.a. Mainland) China.

Russia is the largest country in Asia.

It’s Russia. 77% of Russia lies in Asia while the remaining 23 lies in Europe. Russia is about 6.6 million sq. miles so 77% of that is about 5 million square miles. China is about 3.7 million square miles. 

The Asia is big.