Batman Beyond/Nightmare Fuel

• "Lost Soul". First, the Batman suit is taken over by the cyber-ghost of a dead businessman. But wait, that's just so he can use the suit to be able to put his cyber-soul into the very meatspace body of his grandson. But that's not the HONF, oh no. That comes when Batman defeats the cyber-ghost, still in the Batman suit, causing his "program" to be wiped out, slowly. The cyber-consciousness get degraded, his mind devolving from teen, to kid (reciting basic arithmetic, no less), to infant, and then... gone.
• "Earth Mover". The dessicated, rotting and still alive corpse of a man who was buried in a cave-in along with toxic waste who managed to learn to control the earth.
• "Splicers" is purely built on this. Remember how in Batman: The Animated Series Kirk Langstrom and Emile Dorian's experiments? Well here we see it's become a fad. We also see kids have altered their body's, which is very unnerving. And than the head of it, Dr. Cuvier, overdoses Terry on vampire bat DNA. We see Terry beg for help as he slowly turns full bat.
  • And there's how Terry overdoses Cuvier on random DNA, so he turns into a monstrous...thing. Words don't describe it.
• Patrick from"Rats" who takes neglected kids in. Unfortunately if you so much as complain, he takes it as mocking and feeds his victim to his rats, as Dana finds out. And he's done it many times before, to the point it got reported on the news.

Patrick: You made fun of me! You're just like the others!
Dana: And...what happened to them?
Patrick:They don't make fun of me any more.