Demon and Demon
Majin tantei Nougami Neuro has one of the Best use of the trope: the monsters/demons are more humane than humans.
Sicks technically can't be called Even human, as i may say not only in his behavior but in his biology either, and that works explendid to highlight the developt Neuro has reached to this point, almost completly a death corpse fighting for something so irrelevant at the start for him as humans where outside of being his food.
He was and Will be in My brain forever for being just such a bastard from the start to the end of his role in this series, the definition of evilness, the dark Messiah of his world, Also i know that a Lot of people are bored of the antagonists or villains of nowdays having a reason or a backstory that would make us sympathise with them at least a little, for me it's not a problem at all, since the villain because villain it's Boring for me, but Sicks just did that trope justice in a excellent way on his execution, he was refreshing Even thanks to that.
But well i'm happy that he it's dead he deserve it, one of the most satisfying deaths of a villain i have seen in all of My life.