I agree Hitler was a terrible general and his blunders helped us win the war. The worst to me was his decision not to make a maximum effort to take Moscow and Leningrad and instead send the bulk of his forces off toward the Caucasus, leaving a huge exposed flank for Zhukov to attack. Had he concentrated on Moscow, he might have been able to knock the Sovs out of the war.
There was a fairly recent story that British intelligence considered whether to mount an assassination mission against Hitler and one of the arguments against was that Hitler's blunders were shortening the war.