The victory took the Viola—visitors to the Giuseppe Meazza—up to top spot in the Italian standings.
Despite only conceding one goal and remaining unbeaten in their opening five games, Inter were torn apart within 25 minutes by a Fiorentina side that look revitalised under Portuguese coach Paulo Sousa.
They were 3-0 up within the blink of an eye following an opener by Josip Ilicic and a double from former Blackburn Rovers hitman Nikola Kalinic.
Slovenia international Ilicic opened the scoring from the spot after being fouled by his compatriot Samir Handanovic, before Kalinic doubled the lead after the keeper failed to deal with another Ilicic effort.
The Croatian forward added another from close range following a superb cross by Alonso Mendoza before prompting Miranda into an error which saw the Inter centre-back given a straight red card.
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Mauro Icardi pulled one back for Roberto Mancini’s side on 60 minutes but was unable to inspire the Nerazzuri to the victory.
Kalinic completed his hat-trick to ensure that Fiorentina take top spot after seven matches.