There has certainly been a lot, but my gut still says China or maybe Soviet Union.
It really depends on how far back you are going and what criteria you're using to ascribe responsibility for any given type of death.
For example, if a CCP guard kills a Uyghur prisoner in one of the camps that's obviously a death under the CCP, but if China creates an economic crisis in some country via its Belt and Road debt colonialism campaign and someone there subsequently dies due to hardship stemming from those economic issues is the CCP responsible?