Do KQ's NBO - Guangzhou flights fly full?
If yes, then the addition of China Southern will be a plus as KQ can sell more seats.
If no, then it could be a problem as passengers have a choice between KQ or CS.
Too bad KQ cannot use its 777 to fly another Chinese/Asian route.
Greedy when others are fearful. Very fearful when others are greedy - to paraphrase Warren Buffett