Godzilla vs. Hedorah (1971; aka Godzilla vs. the Smog Monster, as I saw it, in the theater, on its original release), is an execrable addition to the Godzilla mythos. The primary conceit, not to mention the message, which is driven in with a nail set, is a monster, perhaps originating from outer space, that feeds on smog and pollution, and is composed of minerals that can combine and change form when the opportunity arises: Hedorah.
After demonstrating some rather ugly ways to kill people, the local humans try to destroy it using a pair of monstrous electrodes, luring the giant, leering sludge pile between them and meaning to hit it with the output of a power station, but during a tussle with Godzilla, the circuit is cut. Fortunately, a slightly acid-burned Godzilla is able to use the electrodes to convert his chronically bad breath into electricity of the right frequency and help destroy ol’ Smoggy.
Throw in a scientist who lost an eye to the walking vomit-pile and babbles science-nonsense; his son, who has a telepathic connection to our favorite guardian of Earth; a rather unique approach to making Godzilla fly; and some 1970s-style, LSD-influenced digressions, which are probably unique to the mythos, and this one was painful to watch. The models were nice, I must say, but as usual, the characters are flatter than a chunk of cardboard, and the dialog is even worse.
Give this one a miss unless you’re a completist. If you’re a completist, this one may require alcohol.