It is sad to not side with Marcus because she died 3 times being murdered because of the nobles and because of that her lovers decided to let her go be able to be reborn.
What if all the sadness they have Marcus can see and feel it too?
We know that Graham shares a link with him which is maybe Marcus good side, when he was a hero he did it for the good of people and be able to be with Jun but tragedy repeated 3 times!
I would go savage like him if not worse like Dracula in the anime of Castle Vania, lol