China is an economic superpower in the Asian region which stabilizes trade in that region. China also is a military powerhouse and for that reason provides stability in the region as well. The economic and political stability China provides is beneficial to the region because countries are less likely to invade one another.
China is the growing superpower. China sometimes use military force to interrupt the region's stability and this can ordinary happen to a country that has much power. For example, America has been using its military and economic power to bully many small states around the world, hasn't her? I think real stability NEVER happened anywhere in the world if there still have superpower in the world so that it can bully weaker states as they want.
If anything, China has shown to be one of the major forces destabilizing the Asian theater. They have tried to control trade, land, politics, economics, and media in and out of their own territory; even now Japan is having issues with China over minuscule pieces of land when China has gone so far as to deploy fighter jets over these lands (apparently just to assert dominance).