While his intentions were, in his own mind, beneficial to the whole of humanity, in reality his methods were beyond unethical. It's more likely that he had some kind of mental issue or a distorted sense of reality than that he was a genuinely awful person.
“History is always written by the winners. When two cultures clash, the loser is obliterated, and the winner writes the history books-books which glorify their own cause and disparage the conquered foe. As Napoleon once said, 'What is history, but a fable agreed upon?”
Hitler gave life to a downtrodden Germany, revitalizing the economy, which was comparable to Zimbabwe. He also ensured that atrocities weren't committed after his Holocaust. Hitler ensured that the world was united against him, giving Europe a common enemy. And above all, he killed Hitler.
Germany was decimated by The Weimar Republic hyperinflation, cultural degeneracy promoted by outsiders (child prostitution was rampant and open), Germany had legitimate beef with the Jews who betrayed and cost them the war in WWI while benefiting disproportionately from their crushing defeat.
Hitler would have not been that bad if he was doing the best thing for his country. But at the time, about 522,000 Jewish citizens lived in Germany. This means that Hitler was killing his citizens, and therefore not doing the best for his country.