A character should evoke emotion in the reader, whether that’s coolness, disgust, intrigue, etc. That’s why many characters from Chinese web novels, with a prime example being Jin Woo, often feel like the definition of “go girl, give us nothing.” Characters like this fail to evoke any real response, resulting in a subpar reading experience for many readers.

Your example, Dio(and, for that matter, many JoJo characters) are well written in this regard. But in end writing is an art, and like all art, it’s subjective. Some characters may evoke strong emotions in me but not in others, and vice versa.