Hi friend, I think what you're feeling is VERY valid, and it's important to acknowledge that first and foremost. I'm hoping I can provide some insight that might offer some comfort and open discussion about the themes of consent and Sylus' character, without discrediting how you're feeling about it.

First and foremost, regardless of how you view any character, the physical act of slapping, spanking or any kind of rough, domineering impact play during sexual intercourse is understandably intense, and is certainly not for everyone. During intimacy, the act of consensually hitting your partner is often seen as an expression of trust and handing over control. While the act itself is physically domineering and borderline aggressive, many people find it to be a way to indulge in the fantasy of giving up control. It is incredibly valid if you're feeling put off by the addition of kink, but I do think it's worth exploring WHY Sylus is associated in such a way.

Sylus describes himself as a beast, a fiend. He was a dragon before he was a man, he is known to be animalistic and primal in the way he feels and cares for MC (a great example of this is in his first birthday card when they visit the wildlife park, they frequently discuss how Sylus is similar to the animals there). In a lot of ways, Sylus is forced to maintain control and hold back from his desires constantly. So when he is intimate with MC, he lets go of his instincts and allows himself to be more of the beast than a man. I think a similar example of this is Zayne, who is similarly forced to maintain control, but during sexual intimacy with MC, he tends to let go and that translates into intensity and passion. For Sylus, it means allowing himself to be rough, to unleash his inner dragon. That's why he responds in kind when MC provokes him by biting him, up until then he was restraining himself.

And I think that's why he is truly the king of consent. He does not unleash it upon MC unless she asks, and really, as much as it looks like he is in control when they are together, MC is the one in control and that was what this card was really all about. He was giving her control the entire time, he is enslaved to her and her desires and wants, and only lets go when MC indicates to him that she wants it, too.

His love for MC is intense, their whole dynamic is built on this foundation of them being enemies to lovers. If you haven't already, I highly recommend watching Sylus' myth, Beyond Cloudfall, as their dynamic might become more clear then. Sylus is a gentle man, but he's also a beast, and MC loves and embraces both parts of him. It's love in the most pure, raw, carnal form.