Which cocktail is known for its bitter flavor profile?

The Negroni is recognized for its distinctive bitter flavor profile, which is primarily created by the combination of gin, sweet vermouth, and Campari. Campari is a bitter Italian apertivo that contributes significantly to the cocktail's overall taste. The balance of these ingredients results in a complex cocktail that showcases both sweet and bitter notes, making it a popular choice among drinkers who appreciate a more robust flavor experience.

In contrast, the Margarita tends to have a bright and citrusy profile due to the lime juice and tequila; the Old Fashioned, while it can have some bitter elements from the Angostura bitters, is predominantly characterized by the sweetness of the sugar and the richness of the whiskey; and the Bloody Mary is known more for its savory flavors from tomato juice and spices than for bitterness. Thus, the Negroni stands out as the cocktail most closely associated with a bitter flavor profile.