Both are bitter and spirit-forward, but the Negroni uses gin as the base liquor, while the Boulevardier uses bourbon for a richer, sweeter flavor.

Both are strong and whiskey-based, but the Old Fashioned is sweeter and simpler, using just whiskey, sugar, and bitters, whereas the Boulevardier adds sweet vermouth and Campari for a more complex, bitter profile.

Both are whiskey-based and spirit-forward, but the Manhattan uses sweet vermouth and Angostura bitters, while the Boulevardier introduces Campari for a distinctive bitterness.

Both are strong cocktails, but the Paper Plane uses equal parts bourbon, Aperol, Amaro Nonino, and lemon juice, while the Boulevardier is more bitter with bourbon, sweet vermouth, and Campari.

Both are bold and spirit-forward, but the Sazerac uses rye whiskey and absinthe, while the Boulevardier features bourbon and Campari for a more herbal and bitter twist.