Great Monster Yongary (partially lost original Korean version of film; 1967)
Among the most hated of the daikaiju movies, Great Monster Yongary is also the best known of the South Korean monster films. Although it's not the first one of its kind (that honor goes to the long-lost 1962 variant of Pulgasari), it's the first one in color (assuming the first one was in black and white) and the only movie given a dubbed North American release.
When released in South Korea, the movie wasn't well received, but it still got sent to American International to be dubbed and released across the world. This American dub, retitled Yongary, is currently best known as one of the subjects of the recent Mystery Science Theatre 3000 revival on Netflix.
The movie was, until recently, believed to have been heavily cut for the American release, but new evidence suggests only the original language print is partly lost. The Japanese edit ran at an hour and 14 minutes, while the original and now lost South Korean version was at an hour and twenty. The AI print also runs at an hour twenty but is missing the original credits, and the dubbing ended up cutting out some dialogue.
It seems that none of the alternate edits of the movie still exist, the only restoration done to the AI edit revolved around the credits. There is still a 48-minute long fragment existing of the original version, but it is heavily cut and contains no previously unseen footage.
Also of note is the 1999 remake of the movie, simply called Yonggary. The movie was never put onto DVD and its original 1999 edit is believed to be lost as well, but there is still more info than what we have for the 1967 original film.
Another South Korean monster film, Youngster Gugu and Monster Zuzu has a monster with a similar design and has since been given the widely used but innacurate title of Yongary Raids Again.