I know he is pure darkness/evil, but what if he is possession of the x-blade again?
Remember when Aqua was fighting Vanitas/Ven, and he said, "His heart has become a part of mine now", couldn't the same work the other way around?
I am saying that because I assume Vanitas might be in possession of the x-blade again, in which Ventus will have his heart destroyed AGAIN if he is defeated, so I'm not sure if defeating Vanitas will solve anything.