Hitler was to arragont, he had the brightest people in the world as his cabinet, and he made it a policy not to listen to them.
He had the choice on attacking Moscow and Kiev right before the Russian winter started, he chose Kiev which was taken and then the winter hit. Imagine being in Moscow before the winter?
He could have done a better job at fortifying france, and all his generals wanted him to.
All his generals were against attacking USSR, and Ribentrop, Hitler's foreign minister, claimed the USSR asked to join the axis pact.
Remember Dunkirk? The panzers had encircled the army and they could have destroyed them in a heartbeat, but Hitler chose to send in the brand new bombers to test their accuracy. The fog allowed them to escape.
Stalingrad was bloody simply because Hitler assumed the soviets wouldn't counter attack, they had counter attacked after almost every other lost battle thus far in the war, so why wouldn't they counter then?
Operation Sealion was abandoned? Why? All his generals were promising success, and had Germany landed on English soil England would have been driven out of the war.
Germany in the first year of the war focused bombing activities on enemy air bases, the result: Almost instant air superiority by Germany due to heavy fighter casualties before they could take off by the allies. So why did Hitler demand they moved from bombing industry to bombing civilian areas?
When Hitler was in the army, he couldn't advance past the rank of Corporal. He didn't know how to run an army properly and yet he tried to. Had he let those who knew what they were doing run the army and he focused on the politics, then Germany might have won the war...