If you want to destroy the human world because they breed like roaches you are evil right?
The Great Demon Lord Beelzebub III, father of Kaiser de Emperana Beelzebub IV, also known as Baby Beel, is my choice of a villain. He might not be much of a villain because after two tries he first sends his last born infant son Baby Beel and later his first born son Lord En. (yeah, his logic is near to non-existent.)
The Great Demon Lord is an airhead, deadbeat husband (according to his wife) who rather sing karaoke and play games than anything else.
That one time The Great Demon Lord almost managed to give a proper speech and rile up his army:
Seriously though, I had a really hard time to think of a proper villain for this challenge. My mind went completely blank. I do like The Great Demon Lord though but he is probably the worst villain in the world, if one can even call him a villain. Probably not. His infant son is more of a villain than he is.
Beelzebub is the anime. Yes, I have a thing for Beelzebub. There might be more posts with this amazing anime. Just cause, you know, I love it.