and if Stalin and Hitler don't count
Hitler was christian.
The hundreds of his close entourage were christian.
The tens of thousands of german soldiers were christian.
The hundreds of thousands of german citizens who supported hitler were christian.
It is with practically 100 % percent certainty that a christian somewhere threw a jew into a stove.
Hitler's use of propaganda used christian apologist, demonizing/dehumanizing jews. ( Martin Luther )
Nazi propaganda simply extended already pre-existing culturally and christian oriented anti-semitic claims that had existed in Europe for hundreds of years.
Nazi's also targeted other groups that christians would define polemically; people of other faiths, jehovah witnesses, homosexuals. etc.
What exactly about Hitler.. was NOT christian?
Stalin ( a psychopath ) used his political position to violent subdue those that would oppose him or actively spoke out against him. Which included christians, jews, atheist, and well.. everybody
. Stalin placed himself at the head of a kind of state worship, created his own 'miracles' ( promising yields of crops magically ), and exhibited classic signs of other psychotic traits - narcissistic etc. Millions died from neglect, violence, famine, etc.
Was he an atheist? Probably.
Could he be considered 'secular'? Sure.
Now what about any of the above is inherently 'atheistic'?