Italy was it for me. The train station in Rome was crazy. And just Venice in general. I was probably just in the touristy areas, but it was definitely the most hardcore non-stop street scamming I'd been around.
Rented a car out of Munich and they forbade me from driving it to Italy. Said thieves are too common to risk driving, even in northern Italy. Train was simple enough though.
> Venice in general
That's weird because in Venice I never had a single problem, didn't feel scammed or anything, ate in very nice restaurants (I do avoid the tourist shops and restaurants though) and the people in general were nice. I almost felt at home, and many shopkeepers even spoke French, maybe better than English (I am French). I don't think anybody in the street accosted me at all, anyway. I'd go back without any hesitation.
I was just in Rome last year. The only place I really ran into issues was outside the Coliseum. I just said “huh” and mumbled “I don’t know” to every question until they went away. “Where are you from?” “I don’t know.” I think they just thought I was an idiot, or had very limited English, which is fine by me.
I was told later by a guide that if you say “no, grazie” in a semi-convincing Italian, they’d assume you’re local and leave you alone.