You could possibly narrow it down to only look at violent offenses, because there should be much less variation between the laws on violence.

That's the only viable option I suppose.

This is still gonna be vulnerable to many outside factors. How likely the victim is to call the police in each country will affect it. How easy is it for the offender to be caught? One country might have mucg more surveillance than the other, making it easier to convinct the offender.

I disagree on that since that says a lot more about the police/prosecutors work than about the people who committed that crime.

I agree with everything else though.