Rwanda would come really, really close. It's arguably worse because those people weren't collateral damage — their deaths were the point of the exercise.
We don't know how many people have died as a direct result of Chinese internal policies and we likely never will. They certainly cannot be believed with any statements about human rights, imprisonment, or executions on any level. I would likely extend that to education due to rampant cheating and the interests of the central government (to look as good as possible regardless of the facts), but that is a separate conversation.
At the current rate, all ~13 million Uighurs in mainland China will effectively cease to exist in a generation or three. They'll still exist in genetic terms, but their culture will have been erased except for small pockets of holdouts, who will be hunted down and assimilated/imprisoned. This isn't to minimize the death toll of the War on Terror, but rather to not allow seriously bad actors to escape the scrutiny they deserve.