Voltage adapters

No, no.
There are two different things here. Voltage converters and plug adapters. Do not get them mixed up.
A plug adapter is used to make the plug on your appliance fit into a different shaped socket.
A voltage converter converts 230V AC electricity as used in Europe into the 110V AC used in North America.
You may need one, the other or both.

QUESTIONS

1) What voltages does your appliance accept?
If it says "110/230V 50/60 Hz AC" (and post modern chargers for electronics do), then you DO NOT need a voltage converter. If it just says "110V 60 Hz AC" then you do need one.

2) Is the plug on your appliance 2-pin or 3-pin?
If it is 2-pin, you need a standard Euro 2-pin adapter, which will work in both Italy and Switzerland.
If it is 3-pin, you need a 3-pin adapter, and these are DIFFERENT for Switzerland and Italy.

If it is 2-pin, you need a standard Euro 2-pin adapter, which will work in both Italy and Switzerland.

The two round pin type C Euro adapter sort of works in Swiss outlets. The Type C pin is the correct spacing and shape but slightly larger in diameter than Swiss plus. We had to sort of push the Type C adapter into Swiss outlets.

Our Swiss hotels did have loaner adapter plugs for Euro to Swiss. My 230v iron had a Type F Schuko grounded plug that needed a Swiss adapter. If your Type C doesn't fit, borrow a Euro to Swiss adapter from your hotel.

Edgar, you must have had a bum adapter. A standard 2-pin Europlug does fit Swiss sockets.
A French or German (Schuko) 3-pin plug has thicker pins and does not fit. Newer Swiss sockets are recessed, so you can't even try to fit it in.

I think the problem is that some of the adapters sold are manufactured outside Europe and are the wrong size, either thicker pins, or too big for the recessed sockets.
The standard 2-pin plugs sold in Europe, such as you find on phone chargers, fit the French, Schuko (German), Swiss or Italian sockets. 3-Pin plugs are different on these 4 systems.
UK is a different matter, totally different.