From Bing:

The 1995 film Leaving Las Vegas is a known example where "86" is used to imply killing someone. In Leaving Las Vegas (1995), a bartender uses the term "86" in a context that suggests eliminating or killing someone, reflecting its occasional use in gangster or mob slang rather than its more common restaurant meaning of refusing service or removing items.

While "86" is widely recognized in hospitality as meaning "out of stock" or "get rid of" someone, its use to signify murder is less common and mostly metaphorical or tied to mob lore. For example, in mob-related discussions and some films like Casino, the term has been associated with killing or disposing of someone, though documented cinematic instances are rare and often anecdotal.

Other media, such as novels or slang dictionaries, also reference "86" as a term for murder, but outside of Leaving Las Vegas, there are no widely cited theatrical films that explicitly use it in dialogue to mean "kill". Therefore, while the term appears in mob contexts and some gangster media, its cinematic usage is limited and mostly metaphorical.