Forgive this for being simplistic.
The successful assassination of Hitler early in the war would have done wonders for the Reich.
Less economy/ trains tied up in the ‘final solution’.
Liberation of eastern Europe/ White Russia/ Ukraine rather than war of extermination against the ‘inferior’ slavic peoples. This would have lead to much less partisan activity behind the lines, and would have provided easier access to food/ shelter/ conscripts etc.- rather than a population that quickly learned it had to resist or be killed.
Sober choices regarding Stalingrad/ Kursk/ Battle of the Bulge etc. These battles cost the Wehrmacht hundreds of thousands of lives and thousands of armored vehicles/ artillery/ aircraft. Each loss was another broken vertabrae in Germany’s back. All of them were the result of Hitler’s personal hubris. Stalingrad could have been bypassed- instead the entire 6th Army was consumed and marked the official turning point on the East Front and the war in general. Kursk was pure stubbornness- the Red Army had over 10,000 pieces of artillery prepared, massive anti-tank earthworks, and outnumbered the German armor by over 2 -1, and knowing this Hitler still ordered Operation Citadel to continue. What a dufus.
Less resources spent on ‘wonder’ weapons and V1 &2 (Vengeance) rockets. Negligible effect on the war, large amount of brain power and resources wasted. Again, this was personal and not rational.
As said earlier in this thread, winter clothing for the start of Barbarossa.
Implementation of total war economy. Hitler insisted on having life in the Reich stay as normal as possible. Oops. In the meantime Russian women were flying Yaks and driving T-34s, American women were working their asses off on assembly lines producing Shermans, and all the while German women were getting busy trying to push out as many aryan babies as possible. Another mistake.
Allowing Goering to lose focus on the prize during the Battle of Britain. The RAF was exhausted and all but defeated. A few stray bombs fell on London by mistake, and the next thing you know the Luftwaffe is going after cities rather than the battered British air force. This break allowed them to recoup, and Britain remained alive and eventually became the staging ground for D-Day.
There are a bunch more.
If Hitler had been offed, and his generals had taken control of the state, Germany would have avoided myriad disasters and most likely would have kicked in Russia’s door.
Thank god all the assassination attempts failed.