This might not answer exactly your question, but may explain why this is a (obviously) difficult question to address.

I came across Ron Rosenbaum's book "Explaining Hitler: The Search for the Origins of His Evil" in which Rosenbaum attempts to compile and present all major theories that have been proposed aiming at explaining Hitler. "Explaining" in the context of the book means when and how exactly did Hitler come up with the idea of the Holocaust.

Rosenbaum goes through all major theories that try to explain his actions. He presents theories that range from religious ones (i.e. that he was satan himself), to theories attributing his hatred for Jews due to some incidents that happened in his life (e.g. the doctor who was treating his mother or his strange relationship with his half-niece Geli Raubal who committed suicide allegedly because she was having a relationship with a Jew that Hitler did not approve). He even presents theories that basically forbid the research aiming at explaining Hitler (which if i remember the book correctly is officially adopted by Israel).

For each theory, he presents arguments that support or are against it. By critically analyzing each theory he also reports on Hitler's early life from which some aspects of his character can be inferred. IIRC Rosenbaum does not adopt any of the presented theories and asserts that the issue is still open.