[Conquering hearts is much harder than conquering lands and dimensions. In fact, in every conquest and every campaign, the thing worth watching out for the most, is the hearts of the people you've subjugated. Simply put if you're unable to get them to have at least a basic acceptance of your rule, then everything you conquered and gained would be for naught.
Every fight is important, but none more important than this. Because if they can't love you, you must make sure they fear you. Because both feelings are the starting points, branching out to more complex emotions based on how you rule. Love can lead to hate and fear can lead to adoration. You don't have to be kind and benevolent, let them think you are. If you have to prove your strength to them again and again, then do it once, and in such a manner that fear would thoroughly suffuse their bones and break them.
thanks for reading and God bless you all