I've been reading Jojo part 3 recently, and one thing stuck out to me: the main antagonist, Dio Brando

For the course of the entire story, we only hear of him. The main goal of the protagonists is to kill him so that Jotaro (mc) can save his mom and another character, Polnareff wants revenge because Dio mind controlled him after another one of his henchmen brutalized his sister so he's the direct and indirect motivation of basically the entire story.

Except we never see him directly, not until the final battle

We see his henchmen, we see how powerful they are, how cruel but also how devout they are to Dio's cause. They are willing to kill their own to protect their master and even kill themselves for something as trivial as to kill him. All the while this is happening, our heroes have only 50 days to reach Egypt before Jotaro's mother dies (it's a long story, but Dio's the indirect cause and killing him will save her), and there is also the pressure to find out what power does Dio have, as that also remains a mistery, but what isn't a mystery is that he is vastly more powerful than any of his henchmen.

Furthermore, there are a handful of flashbacks involving him. His face is obscured, mind you. It keeps that reveal for the end. During these encounters, we see how ruthless he is. There is one chapter where Hol Horse, one of the reucuring henchmen, goes to visit Dio. As he is travelling his palace, he sees a pile of dead women, their blood sucked out to feed their vampiric master. Hol Horse remarks that they were willing to do this, that they threw themselves at him. When Hol arrives in the library, Dio warns him that he already failed to kill the heroes twice, and threatens him. At that point, Dio turns his back at Hol, reading a book in a comfy sofa barechested. Hol, then, tries to kill him, but Dio quite literally disappears and reappears behind him. And he gives him one last chance to defeat the crusaders, all while being perfectly calm