You do get to crush rebels, also your own allies you can execute if you want to be even more feared.
For instance, say you arrive on a planet to help crush a rebellion. After arriving you are greeted by a group of mercenaries hired by the planets Governor to help the military keep order.
You can talk to them, intimidate them, disarm them. Or, of course, slaughter them all.
As for the emperor, he prefers using force.