I don't want to write Marcus.
Marcus is Jessa's husband. Marcus is... not why Fenris and Jessa broke up, but he's the catalyst. They broke up because she realized that she loved Marcus... because Fenris couldn't deal with her not being his alone. And even if she broke up with Marcus - the possibility is always there. She can never promise that she will not love anyone but Fenris. And Fenris can't live with it.
So Marcus is a catalyst for important stuff. Without this, the Kirayth wouldn't exist. The face of Shayara would be totally different. Fenris would be totally different. Without Marcus, Jessa actually stood a better chance of survival during the Purges. Et cetera.
He has to be there.
But I don't WANT him to. I don't LIKE him. I resent the hell out of him. Because I love Fenris and Jessa. I love that they're best friends and first lovers, I love the way they complement each other. I look at them and I feel this love, their love.
So I hate Marcus. Because he fucks that up. Jessa loves him, but she'll always have this ache from the loss of her beloved, from this painful shift in her relationship with her best friend, first love. And Fenris is traumatized for life - by knowing that her love for him is not as complete as his for her (in his worldview). Later by siring her child, and having to see that child raised as the daughter of this man who's taken Jessa from him - which he entered into willingly, but of course he didn't understand how godsdamn much it would hurt. And then Jessa's death... and Fenris will forever blame himself for that. If he'd been with her...
So I hate Marcus. I hate him I hate him I hate him. And I'm not allowed to hate him! Because if Jessa falls in love with him... I have to find a way to love him. Because otherwise it will all fall flat. It will feel wrong to the reader.
But I hate him.