I think it's interesting that they refer to him and his cards as Supreme King. And no I'm not writing this because of my fandom for Haou Judai. We already know for sure that Zarc likes victory and winning and the ending of Episode 135 confirmed that. So maybe Zarc wants to be the all-powerful ruler of the United Dimension. A conqueror. A Supreme King. And he wants to do it in a violent way that his Dragons demand.

As far as this concept being interesting, I can live with it. If he brutally crushes his opponents in his conquest to become King I think that's interesting. Not super evil but interesting.