I am not aware of any universal scales of offence seriousness, those that I have come across have been culturally dependent.

For example, in NSW Australia there is the Median Sentence Ranking (derived from the average sentence given to first time offenders). The New Zealand Seriousness of Offence scale on the other hand is derived from expert opinion (i.e., a panel of judges) rather than judicial outcomes. Both of these scales indicate the perceived seriousness of the offence predominately in terms of the social perception of the offence seriousness; as far as I know, there is currently no scale rating the seriousness of offences in terms of their potential developmental impacts.