the Koreans?

[mrmod]

The big problem is, that China remains supportive of North Korea.
China doesn't really like the stalinist communist regime in North Korea any more.
But China fear the result of a reunification of the two Koreas, which would likely follow the example of the reunification of the two Germanys, whereby the rich democratic state absorbs the poor communist state.
A reunified Korea would be an economic manufacturing power house, with millions of North Korean labourers able and willing to work for wages that would be quite competitive with the Chinese wages.
China does not want a prosperous manufacturing powerhouse, capable of beating it at its own game, right on its border.

And as long as China backs that horrible North Korean family dynasty regime, the Western nations can't really do anything about it.

That is a very interesting point, I have never thought of it in that way.