Is it really needed to defeat mundus or could Dante have beat him without it? Or is if like force edge where it's needed to tap Into that "next level" or to at least achieve it. Like could Dante become as strong as he is post1 or even during 2 without ever coming into contact with force edge? Because then he woulda been screwd if vergil didn't roundabout give it to him for him to use in 1 against mundus