Waterloo : not a blunder. I know that the english like to stick to that legend by the angloallies army was the only winner and that it smashed the french army (in that case the angloallies army is often transformed in English army alone
) In fact the angloallies army was close not to be defeated tactically (would have much more looked for a stalemate) but ratherwas close to fall back on the road to Anvers. Wellington himself gave these orders around 16-17 PM. Have the prussians been late a little more, it would have been a strategical victory for Napoleon as it was planified (forcing the Angloallies to retreat and eventually re-embark and afterthat take care of the Prussians).
the battle itself was poorly conduced from Napoleon standard though but the strategical move with lower number of troops was the best that could have been done and may have succeded