Young Writers Society

I'd like some opinions on the deaths of each of the main villains. I'm trying to keep the series aimed at mid-late teens without it becoming to dark and gruesome.

Satan
The colossal, three hundred metre tall demon is destroyed when the protagonist destroys the source of the creature's power. Without the energy to support his own body, Satan collapses in on himself.

Hi-Gro's Death
The Dark Monarch attacks the much stronger hero head on only to be dismembered limb by limb before having his skull crushed by another protagonist.

Lucifer
After their last duel, the protagonist becomes vastly stronger than his nemesis. Beating him in a very one sided fist fight, the hero grabs Lucifer's heart and proceeds to disintegrate him. This ends the sort arc for the first half of the series.

Dread
The alter ego of the hero, he gains his own body. Finally free of the protagonists influence, Dread takes control of an aggressive alien race and wages a war with his alter ego and his forces. After a devastating duel results in a stale mate, one ego not being able to kill the other, the hero, Irin, kills himself knowing that Dread will also be destroyed as they share the same soul. Shortly after Irin's suicide, Dread evaporates as their shared soul departs. This ends the series.

Killing off any character, in and of itself, usually isn't a problem (like, you can do it however you want and no one will probably question you so long as it makes sense). Of course, there's that part: it has to make sense.

Kill anyone in whatever way you think best suits the story, just make sure it's a logical death given the conditions of the world and the abilities of the hero in comparison to those of the villain. A lot of times writers will make their heroes "all powerful" or discover a way of becoming all powerful just in order to off the villain.

The only two deaths that concern me this way are the second and the third, because there isn't a lot of context to why the hero is so much more powerful than these villains who are presumably really powerful and have a lot of control over the world at the times of their deaths. If the hero has always been this powerful, why wait until now to off the villains? If the hero isn't really that powerful in comparison to the regular person, why hasn't the villain been offed already by someone else? How did the hero get their power? Did they spend a lot of time training and developing it? Are they gaining it by the assistance of others, or magical objects? Whatever it is, so long as it makes sense for the hero to have gained this power - and for the villain to have survived this long without being taken down by anyone else - then you should be fine!

The only other slight concern is the first death, with the power source the hero destroys. Personally, if I were a villain with my One True Weakness being a dinky little power source that someone could easily sneak in and destroy I would hide that thing in the deepest darkest depths of the world where no one would ever find it. Or I would keep that thing hidden on my person at all times because I'd really like not to die. So just make sure that the power source isn't too readily-accessible! No villain would just leave that sort of thing lying around without, like, legions of the undead protecting it or something.

Just keep logic in mind when writing, and your deaths should work out just fine! Happy writing!