Was Hitler objectively bad?

[Minimalist]

I think Caesar greatly exaggerated his toll to impress the gullible, so to speak, but blood thirsty Roman plebeians that was his political base. This was a man who wrote of his own greatness in the third person. The toll of Genghis Kahn was also probably greatly exaggerated. There was a total of maybe 100,000 mongol warriors in Genghis Kahn's army. The multimillion death toll was simply not credible.

The more important difference is both Caesar and genghis Kahn incurred their toll in direct support of their military campaigns. Neither killed on a large scale purely out of unwillingness to share the earth with some people.

All ancient stats must be taken with a grain of salt...or a dump truck full of salt.