Which battle is considered Napoleon's greatest victory?

Austerlitz, on 2 December 1805 - the first anniversary of his coronation. He faced a larger Russian and Austrian army and deliberately made himself look weak, abandoning the high ground of the Pratzen Heights, thinning his right flank, and even opening negotiations to suggest he was worried.

The allies did exactly what he had invited them to do. They came down off the heights to roll up what looked like an exposed flank, and in doing so hollowed out their own centre - at which point Soult's corps, hidden in fog in the valley, went up the slope they had just left and cut the army in two. It was over in a few hours.

Two things make it more than a clever trap. He had chosen and studied the ground weeks beforehand, having marched an army from the Channel coast to central Europe in a matter of weeks by a route planned in advance - the logistics were the real weapon. And the victory broke the Third Coalition, ended the Holy Roman Empire within a year, and gave him the position from which almost everything after it, including the eventual overreach into Russia, followed.