technojunkie

I doubt it's the severity of the crime, rather I think the existence of a crime is all Nin needs. He seemed to fixate on 'criminals' that could "dabble in arts that could return Desolation to this world." I think he may perceive that he can't visit 'justice' on surgebinders that have committed no crime, but is committed to preventing surgebinders from manifesting. Take Ym for example; Nin mentioned him living a clean life. This tells me he spent a lot of time finding a crime to convict him over.