A ruler should be feared because he could be abusive and he could be ruling like telling you what to do all the time and you would need help and you can't even leave the castle and you would be terrified but i am not saying that all the rulers or kings are all like that because some of them are nice.
Sure you can have a dictatorship and a secret police and a reeducation camp. People will be in fear always and will obey you.
What happens when someone doesn't fear you?
No one will miss you when you are gone. No one will fight for you they will welcome the coup. Stalin with all his power lived in fear of being killed. No one liked Stalin and he knew the people wanted him dead.
Or you can be loved by the people. They will worship you and will fight for you and your family. And they will not let any harm come to you. And when you die your will never be forgotten but remembered as a great ruler.