I think one of the things that makes Sylus such a strong character in terms of depth is his first appearance. The incredibly intimidating, aloof, dominating, and morally grey first "villain" love interest that we're introduced to is not only built up by the set up of his reputation and crimes, but by the way he treats us. He's forceful in a way we're not used to mc being treated- clearly searching for something that we don't understand and he doesn't ask about. And, with the context of having lost Caleb right before his introduction, Sylus comes off extremely jarring (rightfully so) to mc. He's scary! He uses his evol on her to establish physical connection, mc is so put off by Sylus entirely that he's the one love interest we've had that she struggled to resonate with (so much so to a point that it's a pivotal part and hurtle in the exploration of their relationship).
And when that is explained to him, he changes his approach entirely and the real and careful side of him we know starts showing after they're locked together. Sylus and mc's story shows how much he regrets the way he initially approached her- that he made the one person who's ever known him actually fear him because of him. I'm sure it shook him a lot. All of that plays into his character being the personification of the intimacy of consent and patience. You can see him genuinely make the effort to have mc explore her own comfort and autonomy around him- letting her come to him when she wants, letting her find out things about him that she's curious about, giving her gifts of peace and support. We start to view him as endearing and patient, unexpectedly soft, and so eager to be with us. I could talk about this for hours.......but Sylus is just so interesting. Every part about him is something you can find the source of directly and come to an understanding about him. He's the exact opposite of what you assume about him when you first meet. He's such a strong subversion of expectations it's insane to me that he's just in a gambling dating game. So many people would fw him so heavily. He'd be so popular men would unironically hail him as a red/blackpill figure.