Most underrated villian?

Chandell (Liberace)

I think I'd go with Cliff Robertson as Shame. That character cracks me up.

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Cliff Robertson played Shame twice. And the second time was in 1968 -- when Robertson also won the Best Actor Oscar for "Charly." That made him perhaps the most important actor to ever play a Batman villain at the time he played the part.

There were other past Oscar winners. George Sanders(Best Supporting Actor for "All About Eve") as Mr. Freeze comes to mind. And there was a FUTURE Best Actor Oscar winner in Art Carney(The Archer for Batman; Harry and Tonto for his 1974 Oscar.)

Class act villains!

King Tut!!!

Lord Fogg

If there's a one villainess that I find underrated, it'll have to be Siren from the third season. The actress who played her was so much fun. Not to mention quite alluring.