V is never seen speaking anything but English, and given the whole 'no memories' thing, I suspect that's all he speaks. But he's mysterious that way.

Dumbledore speaks English, German, French, Mermish, Gobledegook (yes, that's canon) and probably a bunch of other weird wizarding languages :P.

Italy speaks Italian and English for sure, probably also German and Latin (from living with Austria/the Roman Empire, respectively). Some regions have co-official languages, so he also speaks: French, Ladin, Slovene, and Sardinian.