Nope, the only real reason Germany lost was because of the I AM RIGHT, I'M FUCKING GOD, MY REICH WILL LAST 1000 YEARS JEWS AND COMMUNISTS MUST ALL DIE, THE SLAVS WILL BE OUR SLAVES, PURE AYRAN RACE! mentality the Austrain nutcase had. He killed anyone giving him advice other than "Good plan mien furhur" and made the worse battle plans (albiet Blitzkrieg but that doesn't work against a prepared enemy) that most dictators do.
If anything I'd kill Hienrich Himmler, the man who created to the solution of the Jewish problem, the Nazi Death Camps. He also was head of the secret police (or Gestapo) and was Hitlers right hand man. If Himmler was out of the picture the Nazi's would still be using inefficent methods (firing squads and such) to kill Jews, it would still be a massacare but not on the scale it was. I also doubt Hitler would get replaced by Himmlers replacement because the asshole was a fucking paranoid and delusional fucktard.
Killing Hitler would also do nothing to slow down or damage the Nazi war machine, it could only benifit it because the prick made such terrible strategies. Hitler proved what could happen if you push a country around for too long, Hitler gave his people hope and gave the rest of the world the finger on their behalf. He rebuilt their economy after the high taxes the Allies made Germany pay and took back their original lands. Nazi Germany needed to happen, or it would be something else. History shows us that unstable countries like 20th century Germany are most likely to become dictatorships.