Napoleon has had so many words written about him that he has become a byword for virtually anything you care to name. That has the added benefit of making him an exemplar of various moral lessons, which is useful from a human nature storytime point of view.
1. He didn’t know when to stop. Conquering Egypt, Italy, most of Germany, and Austria repeatedly? Fine. Walking to Russia? Bad idea. Learn when to stop.
2. All process, no plan. He was a furiously energetic person and undoubtedly good at what he did, but like a lot of military dictators (Caesar, Alexander), he wasn’t really sure what he wanted to achieve. Conquer things certainly, spread the ideals of the French Revolution when it suited him, maybe. But beyond that? He put very little thought into the sustainability of his empire and the over-reach caught up with him.
3. He enthroned his incompetent siblings. Don’t do that.
2 is very much a subset of 1.
Perhaps it’s better to be modestly talented with clear, trivial goals, than to be extravagantly gifted with no idea what to do with it? I’d still swap places with him in a heartbeat. Even retirement on Elba seems nice.