Bonaparte was regarded by all of Europe except France as a megalomaniac cruel tyrant - until about 1812. By the end of that year, there was a powerful anti-Bonaparte opposition developing in France also. The carnage that accompanied his reign/rule/administration came to be feared and hated by the French themselves once the glorious days of repeated victory were passed. Unfortunately, the French and the Allies through the Congress of Vienna were unable to provide a viable and credible alternative head of state, so that Napoleon-nostaglia returned within 10 years of his death.
However, Bonaparte did introduce innovations not only in France but throughout Europe and the western world, and they are noteworthy. First, he provided a rational basis for weights and measures instead of the thousands of alternative measures that had been in use for centuries. We call it the Metric System and it works well in all of science and technology, and in commerce except in USA and a few other places.
Second, he introduced an integrated system of civil and criminal laws which we call the Napoleonic Code. Some parts of it have been problematical (notably the inheritance laws) and need reforming, but it has stood the test of 200 years, and is well understood. Even the later monarchies and republics in France continued to use the Code; so well was it thought out.
Third, he introduced the Continental System of agriculture and free trade between (occupied) nations. It remains as a model for the European Union and worked well in its own day. Even the Confederation of the Rhine, which led to the creation of the Zolverein and then to a unified Germany, was based on Bonapartist principles. I don't think the Germans or anyone else is willing to recognise this intellectual debt today.
Fourth, he promoted French science and learning which had been damaged so badly by the Revolution. Medicine, chemistry, physics, astonomy and economics were all encouraged so that French higher education became a model for the century - to be emulated by any modern country with pretentions to culture.
Despite all these, Bonaparte was a mass murderer; of the French as well as other peoples in Europe. He engaged in military campaigns, backed by an elitist philosophy, to extend French hegemony and can be recognised today in all that was wrong with Nazi domination of Europe and now in USA plans for the domination of the rest of the world.
For a short time, he was a military and administrative success but his legacy was one of poverty, defeat and a distrust of the French. He seemed to offer a glorious change to French history, in which the French became winners of wars. In reality, he was just another winner of battles but, ultimately, he confirmed the French experience of losing every war in which they have engaged. Such a pity for a man of potential and flair, but his early success simply went to his head and he seemed to believe that he was invincible and omnipotent. That's a good definition of a megalomaniac, don't you think?