Even better than a villian you can hate is a villian that has a personaility and doesn't see themselves as evil. Of course acting that can be difficult.
I think the sun went nova.By the way, what did happen to the Dilgar? It seemed implied that they were completely wiped out- if so, how? Even after losing a devastating war, some remnants of the population survive. The only way to wipe out a species completely is with a supremely contagious incurable airborne disease with a 100% fatality rate (like the Markab).
Wouldn't they have known about their sun going nova for decades, even generations before the war?