If he had simply stopped after taking back historically German territory from his neighbors (and did it on the sly), he would have avoided war, or at least kept Russia off his border and forced them to strike first.
If he had captured the Brits at Dunkirk instead of letting them be rescued he would have gotten Britain to surrender.
If he had dumped all the Jews and Gypsies on boats to Britain or in Polish territory he could have avoided concentration camps.
If he had engaged in a campaign of sabotage in his enemies territory he could have degraded their warfighting ability and assassinated leaders who were pro-war.
If he had sent light infantry to lead insurgencies in colonies, he could have split British and French forces and kept them off him long enough to defeat Russia.
If he had used Russian auxiliaries embedded with German light infantry, focused on insurgency/sabotage/assassination, and made better use of propaganda (war of liberation against communism instead of war of annihilation against non-Germans, kill your officers and surrender) he could have caused an uprising against Stalin.
If he had gave his commanders more freedom to set goals, strategy, logistics, and tactics he could have avoided a ton of blunders.
If he hadn't killed so many Germans he would have had more manpower later in the war.
If he had kept up military production -especially of defensive armaments - then instead of invading Russia to preempt Russias planned invasion, he could have (along with earlier points I made) let Russia instead invade Poland and sold them weapons. When Britain inevitably sided with Russia, he could have used that as evidence that Britain is a bad ally and gained Poland as an ally, and maybe made the French doubt Britain.
If he had focused on annihilating the RAF after Dresden instead of retaliatory bombing of civilians, he could have destroyed Britain's offensive air abilities and kept the moral high ground.
If he had consolidated his superweapons research he could have beat us to the atomic bomb.
If he had allowed actual mathematicians and engineers to design his cryptographic systems instead of dilettantes, he could have kept his codes unbreakable for the entire war.
Basically Hitler was an a.utistic micromanager and he dun fuked up.
