I would say Aloyse Von Roddenstein (or Rodney for short) from Phineas and Ferb. During the majority of the series, he was previously played for laughs alongside his rival Heinz Doofenshmirtz. But it wasn't until the special Phineas and Ferb Save Summer", that his goofy side was nothing more than a facade to hide his true nature as a power-hungry tyrant bent on destroying lives for his own pleasure. To that end, Rodney formulated a more dangerous plan to send the entire Earth into a new Ice Age based on one of Doofenshmirtz's successful schemes. Now I would grant the fact that the series is played up for pure comedy (I mean I loved the show), but there was nothing funny about Rodney's scheme as it would technically endanger billions of lives. Heck, Rodney didn't care about the disastrous results as he wanted to make a petty point about showing who's in charge, even disabling the reverse process of his machine to ensure that his plan won't fail. So technically, that would be quite vile for anyone in the series, even Doof himself is uncomfortable as he voiced his objections to Rodney's plot.