Reboot of old topic.
Basically, a villain in a formerly light or comedic series who is played completely straight, in order to display a mood shift toward the dramatic. He may Kick the Dog
or Rape The Dog
in order to show he means buisiness. In webcomics, this may be a symptom of Cerberus Syndrome
(not sure if that topic survived either)
Typically the Big Bad
or The Dragon
of a series.
Legato from Trigun.