Besides the little people that were in the republic in this giga fight and lived to tell the tale (and weren't afraid of what the Empire would do to them) which is to little, no one would know that once somewhere In 0 BJE (Before Jedi Extinction, but people wouldn't know how are the B,J and E translated, they would just call it BJE) their king took out republic and made every single one of their lives extremely bad, but not in a way they can understand it because Vader would be still afraid that someone would do a Rebellion, hardest to beat than the one we know, cuz he knew that, if 1 Rebellion started, even the smallest one that's possible to happen, more and more would follow, and his Empire would never be the same again. The Empire would start to lose power until he accepts his lost, and he would pay really expensive what he have done. So, his soul would never truly rest again, he would always have in mind his worst fear, even worse than the fear of death, even worse than the fear to lose a person he loves, the fear of losing everything he built in his life
