I couldn't find another thread on this subject...dead actors/actresses who were at least once a villian on the 1960's Batman TV series. From recollection I come up with...
Frank Gorshin (Riddler #1)
Cesar Romero (Joker)
Burgess Meredith (Penguin)
Art Carney (Archer)
Victor Buono (King Tut)
Roddy McDowell (Bookworm)
Liberace (Chandell)
Vincent Price (Egghead)
Milton Berle & his huge wanger (Louie The Lilac, & his huge wanger)
Shelley Winters (Ma Parker)
David Wayne (Mad Hatter)
Otto Preminger (Mr. Freeze #2)
Roger C. Carmel (Col. Gumm)
Carolyn Jones (Marsha, Queen Of Diamonds)
George Sanders (Mr. Freeze #1)
Feel free to add.