You are right to point out that we usually use the noun "criminal" more to refer to someone that makes a habit of crime or makes their living from crime.
And I'll also add that the word "criminal" is often used to imply someone is subhuman. Possibly subconsciously, but it's common to see people outraged by police brutality only if they think an innocent person is the victim. Things like "no innocent person should be treated that way." I think this is the primary objective of the ever-present ad-hominem attacks such as "well he was no angel."
The extraordinary permanence of certain aspects of identity ("criminal", "felon", "rapist", "racist", etc.) in the information age is radically different from how identity has worked for the past 100 years or so. The possibility of "starting over" is gone.