I couldn't decide what type of dragon I wanted to write, so I decided to do a Rise of Skywalker and now my dragon is all the dragons. This isn't actually hard to achieve. The key idea is a character that shows a different facet of themselves, depending on how people interact with them.
In practice, that means my dragon, despite his above-average-human knowledge and wit, is also an impulsive brat. Consequently, the cliché draconic greed is replaced by an "awesome" borderline-unhealthy attachment to various objects, which might or might not include people (like close friends) and places.
Now that opens up a whole new treasure trove of potential conflict. For instance, you might steal a dirty book from the dragon's lair, then the dragon chases you for miles just to get his favorite book back. In the end, everyone's left dumbfounded that the dragon threw such a tantrum over something like that.
This behavior is tiresome and after a point, scary for a parent when their child does it. Just imagine how utterly terrifying it becomes when the one having a fit is a living flamethrower with the claws of a cassowary and the jaws of a Nile crocodile. It might actually be enough for some to conclude that it's for the best to get rid of (murder) the dragon before he burns down a whole village because the book thief lives there.
At the same time, this allows for endearing character moments as well, maybe the dragon never reads the ending of that book. because that's when the "good" knight slays the "evil" dragon. Instead, he made up his own ending where the cornered dragon tricks the knight and escapes, then later finds a far-away place with other dragons and lives there happily ever after. Or maybe, the dragon really likes to play games like catch and doesn't get mad if he loses (unless you really rub it in).
Thirdly, the villains could use the dragon's impulsiveness to manipulate him (either sending him into a blind rage or blackmailing him), which is pretty good for leveraging the long-term battle.
This all sounds fine and everything. However, I'm afraid the dragon might actually come off as irritating and detestable for the reader, despite the endearing moments. Either because the negative outweighs them or because they actually piss the reader off even more. Compared to my other characters, the dragon is more responsible for his action, which is the point, but I don't want to go overboard and make him unsympathetic, how can I do that?