Say a Nazi sympathizer successfully sneaks into the Potsdam conference as a translator and suicide bombs the negotiations, killing Churchill, Stalin, and Truman in the blast.
What happens next and will be the shape of the world in the aftermath?[/QUOTE]
Well, I'd expect retaliation punishments against Germans to be numerous, and likely with more official sanction and brutality in the Soviet zone and French zone.
Churchill being killed during an election campaign would make Britain be thrown into confusion, but Atlee likely wins anyway. Truman dying would be confusing as well, as he did not even have a vice president. Kenneth McKellar would likely assume the office of Presidency, and he did not seem to be someone who would be as ready to reform as much as Truman did both at home or abroad.