Action Dexter is Dexter's Future Self as an adult. He has big muscles and can fight like a man. He can operate and control weaponry which he uses to fight evil in the dark future where Overlord Mandark rules over the world.
Action Dexter is a big muscular man who has an orange beard and glasses. He wears a black shirt and a white ripped lab coat. It's revealed he has gone bald and that Old Man Dexter was actually wearing a wig.
Unlike young adult self and older self, Action Dexter is pure epic as after years of abuse from his most hated rival, he decided he had enough and quit his job and becoming physically stronger.
Also, just like his counterparts he appears to have issues with his sister as shown when he was shocked by her sudden appearance. He also has his counterpart's tendency to complain as he stated "I wanted to be the one to save the future" after Dee Dee did so.
- He still has Dexter's accent.
- He is the only one of Dexter's future selves that has not been seen in any other episodes besides Ego Trip.
- He and Action Hank have many similarities and traits.
- Action Dexter, unlike the other Dexters, was not voiced by Christine Cavanaugh. He was voiced by Jeff Bennett instead.