1. The Sheldon Brown nut-washers-bolt method (see above) is the best.
2. You could always use a Dremel to reshape the flats on the cup.
3. Sometimes applying just a bit of (in your Italian case) clockwise force, followed immediately by an abrupt jerk anticlockwise will do the trick.
4. I wonder if a prior owner applied Loctite to the threads, as I have had to do on a couple of French and Italian bikes I have owned. (There is a good reason the Brits, Swiss, and everyone else use a LH thread on the drive side.)
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069