Great Leap Forward, Korean War(NK had support from China to kick it off), Chinese civil war.
I see no reason to limit to post 9/11, but if you wish, then Covid is completely China's fault for lax preventative measures and killed more than 900,000.
By your logic, Congo should be topping that list for introducing HIV to the world and causing more than 40 million deaths. That sounds ridiculous to me, but hey whatever floats your boat.