wrongdoerformal
She is a persistent offender and has been arrested five times this year for shoplifting.她是个惯犯，今年已5次因在商店行窃被捕。
Tougher prison sentences may act/serve as a deterrent to other would-be offenders.从严判决可以起到震慑其他潜在犯罪者的作用。
Here at the special school we make every effort to socialize these young offenders.
We're searching for a couple of runaways from the young offenders' institution.
Instead of simply punishing them, the system encourages offenders to modify their behaviour.这个制度并不是单单惩罚犯罪者，而是鼓励他们改正自己的行为。

SMART Vocabulary: related words and phrases

Criminals - general words
abettor
accessory
accomplice
anti-gang
be in the frame (for something)idiom
crook
delinquent
gangbanger
gangland
juvenile delinquent
lawbreaker
lowlife
perpetrator
previous
probationer
recidivist
stalker
wanted
white-collar criminal
wrongdoer

offender | American Dictionary

offender
noun[ C ]
us/əˈfen·dər/
a person who is guilty of a crime:
Because he is a first-time offender, he is unlikely to receive jail time.

offender | Business English

offender
noun[ C ]
uk /əˈfendər/us
LAW
a person who is guilty of a crime:
first-time/repeat/habitual offenderA first-time offender might expect probation rather than a jail sentence.
convicted/alleged offenders
young/juvenile offenders
sex/drug offenders
someone or something that does something wrong:
Concerning damage to the environment, holiday resorts tend to be the worst offenders.