One of the more infamous examples is Vincent Gallo's "The Brown Bunny". Roger Ebert panned it after its initial screening at Cannes, Gallo responded by wishing Ebert's colon cancer would relapse, and Ebert retorted by saying that his recent colonoscopy (in which Ebert was allowed to watch the footage of the medical camera as it progressed through his rectum) was more entertaining than "The Brown Bunny".

Gallo eventually went back into the editing room, and emerged with a new version of the movie. Ebert watched this new version, and afterwards was quoted as saying "It is said that editing is the soul of the cinema; in the case of "The Brown Bunny," it is its salvation."

Source- https://www.rogerebert.com/reviews/the-brown-bunny-2004