I think it’s probably safe to say that none of the big villians Batman fights is really “all there”. For that matter, even Batman isn’t exactly mentally healthy.
However, that being said, the Catwoman and the Penguin seem fairly “normal”, psychologically speaking. Admittedly, Catwoman has that cat fetish, and the Penguin is fond enough of birds to make James Audobon look blase, but, with that exception, they both seem to have fairly normal goals. You know, the Catwoman might want to steal the precious jade cat statue from the Ming dynasty that’s appearing in the Gotham Museum, and the Penguin might want to control Gotham City’s drug trade, both of which, admittedly, are nefarious, but I can’t see either of them doing something like plotting to poison the city of Gotham, which I could see the Joker, (for example), doing.
So, am I missing something here, or are Catwoman and Penguin more or less sane?
Mr. Freeze. Wants to take revenge on those responsible for what happened to his wife. He’s a villian only because he doesn’t care too much about the collateral damage. (Don’t let the godawful movie fool you, as far as I know he never wanted to freeze the world)
Poison Ivy: Ecoterrorist. Sane? I don’t know. Are members of Earth First sane?
Clayface: depending on the incarnation, he or she was sometimes sane, though horribly afflicted.
Croc: Really just more of a brutal thug than a homicidal maniac. Not insane, just a none to bright misanthrope.
There are others such as Lady Shiva, but I won’t go into them.
I think the Riddler’s more-or-less sane, he just has an incredible fear of success. At least, that’s my explanation for why he’d tell Batman all about crimes he’d probably get away with otherwise.
You notice how, even though Arkham is supposed to be a mental hospital, they almost never show or make reference to the use of the standard medications used to treat mental illnesses? I mean, what, a straightjacket and a plateglass window is supposed to make the Joker get more sane? What the heck happened to Hadol?
Catwoman: Sanest of all the villains. Likes pretty things and doesn’t see why SHE shouldn’t have them instead of those who don’t appreciate them as she would, that’s all.
The Riddler: Not insane, just neurotic. Fears success. The Woody Allen of badguys.
Mr. Freeze: Sane, and a genuinely good person at heart, but corrupted by a desire for revenge. A walking morality play. Had horrible things not happened to his wife, he might well have chosen to use his powers for good and be a superHERO instead.
The Penguin: Sane but evil.
Poison Ivy, Harvey Two-Face, and the Joker: all mad as hatters. In their defense, I’d like to point out that they were all exposed to toxic agents.
and one that hard to classify:
King Tut: Sanity personified, except on those occasions when he gets hit on the head by a falling flowerpot. Which for some reason happens in Gotham City every few weeks.
Yes, yes he was. I couldn’t speak to his sanity, but I think the fates of the kids he worked with probably indicate he should be at least considered for the “evil” column. It’s just too neat to be a coincidence.
Doctor: Apparently, he just went crazy. Threw this one cop through the same window fourteen time. Kept picking him up, taking him inside, and throwing him out again. This with four other cops hanging off his arms. You say you know this guy?
Six Pack: Sure, I know him. He’s needed, Doc. Badly. How soon can ya let him go?
Doctor: I dunno about that. We got pretty strict security procedures here at Arkham. On the other hand, you seem like a pretty responsible guy. What the hell, huh? Sign here, here, here, and here, and we’ll release him into your care.
-Hitman: Ace of Killers
Explains a lot, doesn’t it?