To those saying killing Hitler would be bad,
I agree that nobody could predict what would exist in his place, but it is likely that it wouldn't be as bad (how many Hitler's were created in all the countries going through the depression?).
The jews were in a mostly good position before 1933. Sure, there was prejudice and they didn't have their own state, but many were respected members of society, and were safe in that position. Most of world's leading scientists at the time were jewish.
Nuclear weapons would not have been developed for a long time if Germany never went to war. The Manhattan Project took up far more resources than any other single project in modern history up to that point. On top of that, physicists are a very pacifistic group. They wouldn't have done a thing if they didn't believe Germany would do it first, and use it. Bohr convinced the scientists that Heisenberg was working on a bomb under Hitler's orders (it appears now that this probably wasn't true, but nobody knows). Certainly, neither side would have developed the technology without a very desperate war (Japan was not a threat for this) to motivate it.
Also, the USSR gained a lot of territory from the war. The rush for Berlin also increased tensions with the west. Without those things, and without nuclear weapons, the Cold War probably wouldn't have happened.
There are obviously a lot more things to take into account, but this isn't an essay
