I was perusing Newsarama today, as I am wont to do, and took a look at their list of the "10 Greatest Batman Villains of All Time!" Now, Batman's got a great rogues gallery--quite possibly the best in comics (and if not, only second to Spider-Man's), so such a list should be beyond easy. In no particular order, Joker (of course), Two-Face, Catwoman, Poison Ivy, Hugo Strange, Riddler, Ra's al Ghul, Scarecrow, Mr. Freeze, organized crime (e.g., the Falcones, the Maronis, Rupert Thorne). Honorable Mentions: Penguin, Harley Quinn, Clayface, Joe Chill, Darkseid.
I didn't read past number 10. What's a clear indicator that your top ten list of Batman villains is utterly wrong and full of it?