I want to write a fiction TV series inspired by a true love story between a star and his fans except that I'm going to represent the fans as an actual female character and make it a romantic series. Also this star has had a girl making up false rumors (scandal) about him and a I want to include that in my TV series although I still don't know whether to use the same scandal or makeup another one according to what the story needs. So I want to know: Do I need that star's permission first to write that series?
Probably yes. There is a common law form of intellectual property called a right of publicity, which basically means that no one is entitled to use your identity or image commercially without your consent. It was originally developed to protect models whose images were used in commercial advertising without their consent and without compensation.
There are exceptions to the right of publicity. It doesn't apply to satire or to efforts to faithfully recount someone's life in an unauthorized non-fiction biography. It doesn't prohibit criticism of someone.
But, the semi-fictional use that you contemplate is neither satire nor an attempt to make a fully truthful news type report of the person's life and instead is an attempt for you, a third party, to profit from that person's famous identity without their consent.
It is not a copyright, it is not a patent, and it is not a trademark.