It is an expression that is not very common in Italy because it is a misrepresentation of " Criminale ma bello ", a famous quotation by Sapo, which refers to an individual who is labelled as dangerous and harassing towards people. Typical example of this typology is jvasquesgds, often accused of playing a bully role towards the weakest.
Marco: how would you define Jay in just three words?
Marnie: bello ma bullo