The Maid and Her Favorite King of Darkness - Chapter 34

I wonder about one thing, overal in many stories, mangas, there is vilianes and most of the time she is discovered/uncovered early in story, like even before halfway. Most of the time ML is either prince or grand duke ,so basicly only second to emperor.
So what if they would just kill vilianes right after knowing that she is bad one ? Like here, they know something is wrong with Elena, she even told Anna that she knows about story and sie is obstacle, she faked this knife injury erlier, she is speaking with someone when she is imprisoned, she overal show bad atitude.
So what if Claude would just go into her room, cut her down, for convinience pretend that this was due to his curse. And viola, bad one died, even if she was ploting something with someone else he wont be able to get close to emperor anyway. Anna will start feeling more confident, HAPPY ENDING

Option 2:
ML – duke /grand duke
Villianes – prince
Same thing, he cuts him down, obviously they wouldnt execute him imidietly, he would have evidence that prince was ploting something (like in many mangas where prince is bad person and is ploting with some other country to overthrow emperor, there were cases that first prince wasnt crown prince because of his bad charakter but it was his younger brother, sometimes even concubine child)

Anyway, my point is in propably all mangas villians are bad people who whem killed arent pitted by anyone, everyone is happy that they were cut down. So from realistic point of view i wonder how it would work out if ML would just cut down those villians early in tory where they would just know that they are bad. Like here