His assassin was a communist, so that does put him in the broad category of being "anti-fascist", I suppose. But equivalent to "antifa", probably not.
The Italian communist partisans were armed, organised and funded, had headquarters and a command structure, ties to the USSR, and a specific mission to bring communism to Italy (and to other regional countries). This was by force if necessary.
Modern "antifa" is none of that. It is just "against fascism", primarily in the USA, and not "for" anything else in particular. It's like being "against" COVID does not make you "for" gonorrhea or smallpox.
And I was incorrect about the time of day Benito and Clara were executed. Apparently it was afternoon, not morning. Mea culpa.
https://en.wikipedia.org/wiki/Death_of_Benito_Mussolini
Given the abuse of her corpse, now I have to go brush my brain.