Well, a beloved villain in a BL manga could have a charming appearance or unique style. Maybe they show unexpected kindness or have a deep, underlying motivation that's not all bad. Also, their relationship with the main characters can add to their appeal.
A beloved villain in a BL manga typically has elements that challenge the traditional concept of villainy. They could have a code of ethics they follow, or their actions might be driven by love or a misunderstood goal. Their character development throughout the story can also draw readers in and make them root for them.
A beloved villain in a BL manga often has a complex personality. They might have a tragic backstory or hidden vulnerabilities that make readers sympathize with them despite their villainous actions.