Complete Monster: The Evil Hair Maiden in "Slaughterzied" and "Die Die Die!!!" qualifies. Arguably, so does the Serial Bomber after he "leaves half a town smoking in a mushroom cloud" to punishoneadultress.
The Poultry Killer may come across this way to members of any Animal Wrongs Group.
Stupid Evil: The scientist in "On the Ethics." Why, oh why are you creating that monster to begin with? And how will you possibly ensure that you yourself never become a victim? Especially when you forced him to kill his own girlfriend and gave him a perfectly understandable revenge motive?