Thanks for shouting out my disagreements in advance! And thanks for using my idea of ranking the made-for-TV villains!
OK, in terms of made-for-TV villains, my No.1 won't surprise anyone.
1--Siren. Granted, the femme fatale/seductress was a role Joan Collins could play in her sleep by 1967, but I still thought she brought the right amount of menace and believability to the character. Chew the scenery too much with a high-concept villain, and it falls apart. Joan kept the series' most 1950s comic-bookish villain in the real world, at least to some extent.
2--Bookworm. Roddy McDowall's characterization is mild-mannered one moment, out of control the next. But it works. Even his own henchpeople don't seem to know what to make of him at times, and Lydia sometimes genuinely seems scared of him. The writing is good, too. A criminal who is, in essence, a plagiarist.
3--King Tut. He only doesn't rate higher for me because of personal bias AND my opinion that although Buono's ad-libbing and scenery-chewing both were brilliant, I do feel the character influenced the tone of the show toward comedy. Yes, it likely would've gotten there anyway, but I do feel Catwoman, in particular, started being written more Tut-like in season 2, with her snide asides to her flunkies and her 0-60 rev-ups from comedic to evil. As great as Julie was at comedy, her line deliveries in both of those recurring situations weren't as good as Victor's. And really, who could compare to his line readings?
4--Carpet King. Part 1, when he had his moll, Plush, hypnotize all the carpet cleaners in Gotham City, and then try to work on Batman himself, 'Ohhhh, Batmannnnnnn,' was tremendous. And who could forget part 2, when he teamed up with King Tut to rejuvenate an ancient Egyptian carpet beetle. Oh, this was all a fever dream of mine? Oops.

'I thought Siren was perfect for Joan.'--Stanley Ralph Ross, writer of 'The Wail of the Siren'
My hobbies include gazing at the Siren and doing her bidding, evil or otherwise.
'She had a devastating, hypnotic effect on all the men.'--A schoolmate describing Joan Collins at age 17