The 'fallen angel dad' archetype just hits different when he's got a troubled kid to raise. Way beyond just being a powerful cosmic entity, the most engaging version for me is when the whole 'Lord of Hell' thing clashes directly with parenting duties. There's this raw tension between his inherent nature—pride, wrath, ambition—and the vulnerability required to care for someone. I love stories where he tries to teach his kid about, say, ruling kingdoms or ancient magical pacts, but then has to awkwardly figure out how to pack a lunchbox or deal with a teenage rebellion.
It's never just about him being evil or good. The fascination lies in the adaptation. You see this ancient being, who operates on scales of eternity and damnation, having to learn patience over spilled milk or a bad report card. His love often manifests in overprotective, terrifyingly excessive ways—assigning demonic bodyguards to preschool, maybe incinerating a bully's soul—which forces a journey toward something resembling normalcy, or at least a new definition of it. The core of the trope, for me, is that friction: the ultimate authority figure learning he isn't the ultimate authority in his child's heart, and having to grow from that.