User blog comment:Wrath022/Chapter 517: Wendy Belserion, Review/@comment-24489996-20170115045702/@comment-24102956-20170120125522

@CNBA3 Well they either get killed or cursed by their Commandments.

Yes I know. That's why HEROES are there to face and defeat them for a reason. Besides what's a point of being a villain if there are no strong heroes around to battle them and had a reason to exist and make their lives as miserable as possible.

Ask Megamind. He had that crisis when he "killed" Metro Man in the first half of the movie.

Because most characters had other issues to deal with such as handling the Demon attacks around Britannia rather than directly facing the Ten Commandments who could easily ground them to paste.

For your information, Meliodas was cursed to come back to life whenever he dies by the Demon King at the cost of his emotions eaten away and would revert back to what he once was 3,000 years ago: the most evilest and ruthless Demon long before he met Elizabeth (Goddess) and changed for the better thanks to her.