There's this book called Hitler's Table Talk,
a collection of Hitler's private opinions assembled by one of his closest aide during the war. It reveals much of what Hitler really thinks of Christianity, or religion in general.
One historian once wrote that when Hitler was just ascending to power, he used statements like "I am doing the Lord's work," as a rhetoric to gain the support Catholic and Lutheran Germans. He himself wrote in Mein Kampf that "his public statements should be understood as propaganda that bear no relation to the truth but are designed to sway the masses." Says Allan Bullock: "Hitler had no time at all for Catholic teaching, regarding it as a religion fit only for slaves, and detesting its ethics."
Nazi "morality" is influenced by the philosophy of Nietzsche: the "Superman" and the new ethic that is "beyond good and evil." (Not to say, though, that Nietzsche would've approved of Hitler's ideas.)
Hitler considered Christianity to be one of the great "scourges" of history, and he saw Christian ideals like compassion, equality, love of neighbor, etc., as weak.
Other references to Christianity by Hitler in that book:
-- He said of the Germans: "Let's be the only people who are immunized of this disease."
-- He promised that "through the peasantry we shall be able to destroy Christianity."
-- He blamed the Jews for inventing Christianity.
-- He condemned Christianity for its opposition to evolution.
Hitler's leading advisers were also atheists who hated religion and sought to eradicate its influence in Germany.
Another historian, Richard Evans, also wrote, "The Nazis regarded the churches as the strongest reservoirs of ideological opposition to the principles they believed in."
Nazi policies were also very much hostile to religion. They persecuted Christian churches in Germany. Evans pointed out that after 1937 Hitler's government became increasingly anti-religious.
The Nazis also stopped celebrating Christmas and the Hitler Youth recited prayers thanking the Fuhrer rather than God for their blessings.
So, Hitler was very much an atheist. He wasn't a Christian just because he was born Catholic. Many people renounce their faith as they grow up.
So if we're talking about the worse kinds of people, we need only remind ourselves of these atheist dictators and tyrants, mass murderers who had an absolute scorn for the reality of God and the dignity of human life.
But I guess the title of the thread is about Christianity being "the worse religion out there." What is our criterion?