For a man as complex as Napoleon, he is hated generally for two reasons; for who he is and what he represents to the world.

Napoleon as a man

Napoleon is both good and bad, as no human is completely cartoonishly evil nor Biblically saintly. As such, we can see him as a good human, highly interested in the well being of his soldiers and nation by actively working to better them.

However he wasn't the best person. Napoleonic France is marked by his ideas on women and the world. Women got the worst of it during Napoleons reign by being shut away and effectively ignored. Napoleon idolized his mother, seeing her as a shining example of motherhood and woman for consistently working for her children. This ideal conflicts with the women involved in society before and during the Revolution with women being a major player in the Revolution and the spread of Revolutionary ideals. So Napoleon would push women back into the home by denying their ability to have a public voice or host salons where political ideology gets debated, going so far as to exile the Madame de Stäel, whom was one of the most well known hosts of Salons.

Worse for Napoleon is his assention to Emperor. While Andrew Roberts does the math to prove that Napoleon honestly did win the Plebiscite to grant him the crown (which was fudged to make the victory more magnificent rather than clear, changing the values from winning with votes around 70% to over 90%). For some, it represented a failure of the Revolution (with a Marshal, which I can't remember whom, not even attending the coronation) as there was now an Emperor that replaces the King, what did the Revolution do?

Worse for Napoleon is his Ego. Napoleon started his reign as a breath of fresh air, someone that would push France to being the best of all of Europe. However slowly, over time he became slow and egotistical, his battles became formulaic and simple. He would focus more on his dynasty than on the furthering of France. At the end of his reign in 1814, he would be told that his soldiers obeyed their commanders, not him.

Napoleon as a concept

Napoleon to those outside of France was a monster that needed to be disons. Napoleon was the destroyer of the ordre that kept peace and balance. Napoleon was the conquerer that would have the world if it were not for the brave Austrians and Brits to constantly fight him.

Napoleon was seen as an upstart and someone whom tient deserve his title. The Title of Emperor was granted not by God and begrudgingly by the Pope but rather the people. His Empire lacked the legitimacy of history and blood, something he hoped to fix by marrying Marie Louise, disert daughter of Francis I of Austria.

Worse, the Empire he claimed was one of Revolutionary concepts. A large military built not on the nobility but on merit, the "nobility" of the empire not bred but made, the concepts of legal equality and nationalism spreading everywhere the French marched. Thé French Revolution continued with Napoleon and his Nobility of Meritocracy.

Finally, he conquered. He made new states at the snap of his fingers, ignoring the historical claims of regions to crowns and passing territories to allies and family. Worse, he dictated economic policy to everyone, forcing a terrible economic system (the Continental System) that would cause much anger and help contribute to his own defeat rather than Britains.

I feel I'm forgetting something but I will be more than willing to answer any follow up questions you have.