Its no doubt that Joker is Batman's number one nemesis. Whether its something as nonsensical as producing his own brand of Joker fish or something as horrifying as beating a teenager to death and blowing him up, the Clown Prince of Crime's unpredictable nature gives him an air of menace that few of the Bat's rogues gallery can match. But does this unpredictability make him more terrifying than galactic overlords and cosmic abominations?
It's often stated that when super villains in the DCU want to scare each other they tell stories about the Joker. During Infinite Crisis, Alexander Luthor made it a point not to invite Joker to his Secret Society because he was to difficult to control (an affront he paid for dearly). Heck when the Martian Manhunter attempted to rewrite the Joker's thought patterns he almost had a stroke in the first two minutes.
I think what helps Old Jack's rep is that he seems to be one of the more realistic villains in fiction. Guys like Darkseid, Black Adam, Sinestro etc are scary and all but how often would you run into a super-powered despot with a silly name. A mass murdering nihilist with no regard for life on the other hand? That is all too real.
So what do you guys think? Is the Joker the most terrifying villain in the DC Universe?