score:6
I hope you won't be offended when I say your question is a little naive. People have killed one another and worse (yes, it is possible to do worse) and called it good since long before Hitler. His contemporaries recognized this. Churchill called Nazi Germany a tyranny 'never surpassed in the dark and lamentable catalogue of human crime'. He was acknowledging that Hitler was a spectacularly extreme example of something well known throughout history, not a new phenomenon of evil.
However, it is reasonable to ask whether the Nazis knew what they were doing was wrong. I would say they did. They tried to keep the holocaust a secret. Himmler said that it was a page of their country's history which could never be written. He also said that they had managed to kill all these Jews and remain 'decent fellows' because they were strong. This seems like a ridiculous thing to say, but it demonstrates that at some level he knew the killing was wrong, or he would have bragged about it.
This does not amount to remorse. We have a fairly good idea what Hitler's final thoughts were; he wrote a testament saying he had been right about everything, and that he would do it all again. The Nazi leaders who survived the end of the war mostly expressed no remorse. As far as I know only Kritzinger said that he was ashamed.
I don't believe religion is a good thing for mankind, but its literature often expresses my thoughts far better than I could.
Woe unto them that call evil good, and good evil!
Isaiah 5:20, KJV