* DracoInLeatherPants: Exploited to good effect. Louis is a ruthless murderer, but he's a witty and effortlessly charming one too. Almost all of the character tropes are out in full force here.
* HilariousInHindsight: Creator/AlecGuinness saying to Dennis Price, "[[Franchise/StarWars The Port is with you]]".
* JerksAreWorseThanVillains: Louis is technically the villain of the movie, but you'd be hard-pressed to find a viewer who wasn't rooting for him over [[AssholeVictim the priggish, hypocritical and racist aristocrats who make up most of his victims.]]
* MagnificentBastard: [[VillainProtagonist Louis Mazzini]] is the son of the [[AristocratsAreEvil Duke Luis D'Ascoyne of Chalfort]]'s daughter, who was disowned by her family for marrying a poor Italian singer, dooming them to a life of poverty. When the Duke refuses her final wish to be buried with her family, Louis decides to murder off the D'Ascoyne family both to avenge her and gain the title he believes to be rightfully his. Meticulously researching his targets in advance, and quickly learning all the necessary skills, Louis works his way through the eight D'Ascyones in his way. Exploiting their flaws and habits and constantly adapting to any surprises, he ensures that his murders are mistaken for tragic accidents, whilst also charming his way into social circles and rapidly progressing through his professional life. Finally confronting the Duke Louis captures him in one of his own illegal mantraps. Revealing the truth he calls him out for abandoning his mother for marrying for love, hurrying his speech so not to unnecessarily prolong his victims suffering, then stages his death as a [[HuntingAccident Hunting "Accident"]]. Suave, cultured and always impeccably polite, despite his humble upbringing Louis proved himself to be in every way a true gentleman, even indulging the wishes of his own hangman when it appeared to be the end.
* RetroactiveRecognition: The reporter at the close of the film is played by Creator/ArthurLowe.
* ValuesDissonance: Louis and Sibella casually toss around the N-word while discussing "Eeny Meenie Miney Moe."
* SugarWiki/VisualEffectsOfAwesome: The split screen of six Alec Guinesses at the first funeral still holds up perfectly.
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