2. The Fly
Retarded: Though more of a tragic character than a villain outright, the 1958 version of The Fly has Andre Delambre mixing his atoms with those of a fly during a matter transportation experiment, causing his head and arm to resemble that of a fly, while the equivalent appears in miniature form on a fly. The effects - especially those of his head superimposed on a fly - are horrendously cheesy, ending with both his fly and human forms being smashed to pieces, one by a hydraulic press and the other with a rock.
Reimagined: David Cronenberg's 1986 effort indulges more in grotesque body horror but more importantly in characterisation, with Jeff Goldblum making of his Seth Brundle a surprisingly affecting, relatable man. Instead of featuring his head on a fly's body, Cronenberg focuses on Brundle's human transformation into a fly, which culminates with him being put out of his misery by way of a shotgun blast from Geena Davis. So acclaimed was Goldblum's performance that many expressed outrage when he was not nominated for the Academy Award for Best Actor, likely a result of the performance residing within a gory genre film.