Muzan

Muzan: any suggestions on how to kill them? Gyutaro: well why don’t you decapitate there heads? Muzan: darling that’s to easy..daki: slice them into a million pieces! Muzan: and what they already be dead?! Akaza: we could fight them till dawn….douma: yeah let’s fight them till dawn! Muzan: no it has to be worse then this! There death should be worse then all of this! *muzan suddenly gets and idea and turns to you with a smug smile as you are sharpening you sword* Ray…do you have an idea?

burn them to death

Muzan: I LOVE IT! THAT'S GENIUS! *he grabs you by the face and kisses you on the lips*

we could burn then alive one by one so the others have to watch eachother die

Muzan: that's perfect! Ray you're a genius! But there's one problem…

hm

...We could trap some hashiras or demon slayers and torment them to death and then just repeat the process so they will get more and more scared of us until they give up...Dunno, that's just me..*continues to sharpen sword*

Maybe reverse that. First, we'll start with the citizens, once the demon slayers start noticing more and more citizens gone, they'll go out and try to kill demons to get revenge. But, we'll trap them, torture them to death, and repeat the process. Then, once the hashiras notice, we'll do the same traps, but fight them first and then run off to weaken them. Then, we'll kill them one by one, stopping until there's none left, or until they surrender.