I don’t understand how a memory potion affects darkness in one’s soul. Like not remembering you’ve done something bad completely takes away the impulse to do bad things? It means your soul is turned bright white again? This seems pretty nonsensical to me. Why not just give all the villains memory potions then!
I think what they were trying to say is that Bae is not bad or a villain he was just temporarily influenced by the power of the dagger and when his father took that memory away it made Bae forget the feeling of power that the dagger had on him.