The headline says most of it. Tarantino's use of banal dialogue as a device has long since worn out its luster. Most scenes are painful to watch, because you know what is coming: repetition of banal lines that were never interesting to begin with. The excessive amount of gore adds nothing. Certain segments defy credibility in the interest of exploitation-type effect, e.g. the General Smithers bit. The usual Tarantino craft ensures a degree of quality that lands a 6.
Review of The Hateful Eight
