And yet she's also been offered something of a redemption arc, helping to revive hero Jon Snow. With her return to Westeros, Melisandre proves crucial in beating off the wights... until they overrun Winterfell anyway. Despite her convictions and her Valyrian phrases, her "help" is always tainted.
If you don't want to go far as redemption, she's at least sympathetic in her new conflict. She's a priestess whose beauty is held together by a necklace, a fact that will prove important to her fate; without her magic, she's physically crumbling. She did terrible deeds in service of her misguided beliefs, but resolved to make Daenerys and Jon meet. (Though who knows how that's going to turn out -- their being related and everything.) In an interview, actor Carice Van Houten told HuffPost that Melisandre "sees herself more as a matchmaker at this point, bringing together the right people in the right place. Yes, steering people in the right direction because that’s more her job now."
Despite her flaws, she knows her role is to sacrifice herself, to offer her magic as long as she could so that others can better fight the Army of the Dead. In the end, though, her words to Ser Davos prove true in an unexpected way. As she trudges out past the carnage left in the wake of the battle -- which she survives -- Melisandre takes off her necklace, the one thing preserving her youth. While Davos looks on, she quickly ages before dropping her trademark red cloak and falling into the snow. She wrought a lot of pain in Game of Thrones, but it's tough to argue that she's coming from a disingenuous place. Melisandre says that the Lord of Light brought Beric (and his sick fire sword) back for a purpose, which he served by dying. In the end, Melisandre served her purpose, too, which turns out to be inspiring Arya Stark to destroy the Night King. Just when your faith in the Lord of Light is at its lowest point, Melisandre shows why she's certainly not an antagonist. Despite what The Hound says, you can beat death. Now that Melisandre's arc is done, she no longer needs to fight death herself.