Comparatively, Mao killed more people than Hitler and Stalin combined

Britain killed far more than those outfits together,

And Europeans/Christians have killed more than every outfit ever on Earth COMBINED.

Technically, disease-infected people have killed the most people ever. However, for purposes of this, I was sticking with one leader.

Or starvation, something that Britain caused quite a bit of, even the most conservativ estimates for India are astronomical, and they starved half of Iran to death in 1917-19.

There's something of a difference between Hitler starting wars and an extermination campaign against various peoples and poor planning decisions with Stalin and Mao. Besides the numbers for the latter two being a tad exaggerated (A nice round 100 million!), the reasons varied for the deaths, and some would have occurred regardless, albeit exacerbated by their ill-conceived policies. Deliberate killings of their public didn't exactly top their lists.