Man, I love this game.
So, I am trying to reform religion as a norse. For that I need A LOT of piety, but it's ok, because I can execute people of other religions as human sacrifices and get piety.
So my ruler dies, my heir gets the throne of the empire of scandinavia, people don't respect me at all like they didn't my father really and a revolt is iminent just as I am finishing a war for human sacrifices.
So I do the rounds of giving powerful vassals seats on my council and stuff, they still fucking hate me, so I go: "oh well, nothing I can do now" and sacrifice like 20 people to get the piety.
As it turns out, executing prisioners give you dread.
So my vassals, who hold a lot more army than me, who could easily roflstomp me, see me doing this big bonfire of 20 helpess people and are now all terrified of me and just give up.
So I got my piety (still need more, but hey, there's always more christians to burn) AND quashed the revolt just by people going "if this revolt doesn't work he will just murder me"