Imposter

Imposter (Noun): Distinguishing between an imposter and a fraud is very important. An imposter is someone who may not have the credentials to be in a certain area, but who has every intention to do as good a job or better than someone who is properly credentialed. So you may steal from the til, but you'll hopefully put back more than you took by the time the day is done. A fraud is simply someone who is attempting to fool you in an attempt to enrich themselves and screw you over. Source