He wears a piece of Galvan technology known as "Mechamorph Armor" in Ben 10: Destroy All Aliens. The Mechamorph armor wraps around the user and transforms them into a blue Galvanic Mechamorph.
Retaliator was looking for Azmuth when he found that Azmuth's ship had been destroyed by Evil Way Big (which ironically, was Azmuth transformed by the feedback from the Omnitrix) and went searching for the evil To'kustar that he believed to have killed his son.
Retaliator looks like a regular Galvan when he is in his Galvan form. He looks younger than Azmuth because his mind was transferred into a cloned body.
In his Mechamorph Armor, Retaliator resembles a Galvanic Mechamorph and is blue and black and white instead of the regular green and black and white. He can also morph his body into a battle armor mode with his hands as high-powered laser weapons.
Retaliator was shown to be very aggressive, but this was due to believing his son had been murdered and the fact that the Mechamorph Armor makes the user much more aggressive than usual. He was bent on vengeance for his son.
Retaliator has regular Galvan intelligence. In the Mechamorph Armor, he has enhanced strength along with a variety of high tech weapons at his disposal.