A good point: how many deaths is too many? How many can a statesman expect to get away with?
Most politicians/rulers of the time had some responsibility for deaths in war and in most cases it is hard to pin down the blame - in a Parliamentary democracy it is spread pretty thin.
The problem for Napoleon is that he was in sole charge with no-one else to pass the buck to and it is hard to see why he should not be held responsible for the deaths in the Russian campaign and in Spain, both of which he started. The actual number of deaths in either can never be known but I would have thought that it definitely passes the 'too many' threshold.