I haven't read this novel specifically. But generally, a 'villainous husband' in a novel might be a character with complex traits. He could start off seeming bad but then have a character arc where he shows redeeming qualities or there could be a deep love story behind his so - called villainous behavior.
Since I haven't read it, I'm not sure. But it might have a villainous husband as one of the main characters, and probably a female lead who is somehow connected to him, maybe his wife.
To win over your husband in a manhwa, first, focus on building trust. Be supportive of his dreams and hobbies. And don't forget to show appreciation for the things he does for you.
You could start by having an honest conversation with him and expressing your feelings. Maybe try to figure out what went wrong and work on changing those things.