Dex was hired by Michael to get information on his father, Sonny’s, organization, so that Michael can destroy his father’s business. In the process, Dex and Sonny became very close. Dex also fell for Sonny’s step-daughter, Josslyn. They kept their relationship a secret so that Sonny wouldn’t punish Dex.
Dex also works security for Sonny when needed. He has been violent on occasion (such as against slimy reporter Felty) and also heroic (such as when he helped save Anna). Dex is a vet and also ran a gym for his friend, Chet.
He clearly stands up for the little guy and wants to be a hero, but he does a sleazy job for Michael and looks up to his mobster father. Both men are ethically compromised. Time will tell whether Dex can be the good guy that he wants to be for Josslyn.