Criminal refers to a person who breaks the law or who has broken the law. Many criminals have become that way because they had a disadvantaged life, and have not yet been given ample opportunity to overcome those disadvantages. A common theme amongst Conservative crooks such as Jeffrey Archer and Jonathan Aitken coming out of British jails is their surprise at the number of Illiterate people they met while in jail.
We all commit minor crimes like crossing as the road on a red traffic light. But law and culture tend to differentiate between minor criminal offenses such as most of those involving motoring and serious criminal offenses.
There are also rich criminals who use their money to get things the law forbids. There are Conservative, Republican criminals like former |US President, Richard Nixon. He should have gone to Prison but didn’t when he struck a deal with his successor Ford.
As well as criminals who've broken the law of the country they live in there are criminals who break International law. So at Nuremburg after World War II various leading Nazis were tried not for breaking German law, as after all they were in a position to write that law, but for Crimes against humanity. Several ultra nationalists have been tried for, or are wanted for crimes against humanity in the Balkan wars of the 1990s, or for complicity in atrocities during various African wars.