Lex Luthor
I know what you're thinking. "Luthor is one of Supes' greatest foes." He's also got the personality of Dr. Frankenstein and the bank account of Richie Rich. Not to mention he has to wear a super powered exoskeleton suit in order to even go toe to toe with Superman and the glare coming off of that bald dome of his.
Granny Goodness
Seriously? A geriatric old woman? She's about as intimidating as Gusto with an erection. Granted, she's super powerful and could definitely give most supervillains a run for their money, but does she have to be so damn old? I guess I'm being an Ageist, but I prefer my villains to not have to slam down some shots of Metamucil cocktail.
Mr. Mxyzptlk
Yeah, he's got reality warping powers. Yeah, he torments Kal-El on a regular basis. But originally the only way to send him back to the 5th Dimension (and not even permanently) was for him to say/write his own name backwards? Now we know how to get rid of Regis Philbin and Alex Trebek.
The Prankster
This guy is such a cheap knock-off of The Joker, it's not even funny. I'm guessing Siegel and Schuster were trying to capitalize on the success of Batman's greatest foe by trying to give the some general concept to Superman. Alas, The Prankster was and still is just a bad joke.
Toyman
There is absolutely nothing worse than a "supervillain" who's been tinkering with your Tinker Toys and turned them into volatile sticks of dynamite. Or finding out that the same whack job switched out Betsy Wetsy's pee for sulfuric acid.
Ursa and Non
I couldn't lump General Zod in with these two. I'm not a Superman fan by all means, but even I know a badass when I see one. And any guy who can put up with Ursa (who just so happens to be a universal feminist and hates men anywhere) and Non (who pretty much looks like a mentally handicapped version of The Unabomber) is alright in my book.
Please, feel free to debate and ridicule me in the comments section.
CBMTrolls!
Focker=Out!