Responses
I'm not sure, but even if he doesn't care what people think killing all of his subjects after being away for 11 years would not look good in the eyes of the commoners who are already struggling due to the aftermath of the war. He can't use brute force to run a country especially when he's trying to merge them with other regions

Tbh I don't understand why he don't just kill the opposing site when he have the power. It's not like he care what people think of him. I felt like he could burn every enemy he have. He's the emporer. Remind me why please