While it's thought (since there are very few records of the time period for some reason) that his reign was lacking in internal massacres or wars of aggression, you don't conquer 40 nations and more than a quarter of an entire planet's population without breaking a lot of eggs.Is there any evidence he was genocidal? "We offered the world order!" implies he wanted to rule everyone else not kill them.
At no point was he ever not considered a tyrant. And he and his kind were so bad, in fact, that genetic engineering was completely outlawed. Why would that come to be if he wasn't a war criminal in the first place? I mean, we didn't outlaw Germans (and yes, I know that's a silly notion) after Hitler's defeat, and we know for certain what a rotten apple he was.
But hey, if you scrub out all of the bad things Hitler did, and only record the good things, maybe future generations would wonder why the Nazis were considered to be as bad as they were. I mean, he improved the German economy to astronomical heights out of economic despair, created an interstate highway system, created cruise ships for blue-collar workers, created the first Internet (a cable network of radios), created a thriving forestry program, pursued alternative energy sources, encouraged the creation of organic foods and veganism, outlawed vivisectioning, and etc.
He doesn't sound all that bad just from that. But only if you ignore almost everything else he did.