Duo is known as Slur’s master so a lot of people automatically assume he can beat her. Not so! Slur has better sword abilities based on what I’ve seen. I doubt Duo could break her vines. To finish him off she could turn into an energy ball and ram him. Duo can’t beat Slur and he knows it. Luckily they’ll probably never be enemies so Duo won’t have to worry about it. Slur wins.