Shinn Asuka is originally a youth from the Orb Union that lost his family to the ZGMF-X10A Freedom and its pilot: Hikari Yamato, during the First Battle of Orb which provoked him to join ZAFT, it is his rage and young Newtype Sensitivity that drew Kira Li Creuset to him whom confirmed that Shinn and his Uncle were the only remaining members of the Asuka Newtype Noble Family/Clan.
Like the original Shinn Asuka from Gundam Seed, Shinn that becomes a Protagonist as of the Newtype Destiny part of the Newtype Series is a 16 year old youth with short black hair and Crimson eyes, he has a lithe figure which does carry some hidden physical strength that goes well with his fiery personality.
Shinn is far crueller than his Gundam Seed Destiny predecessor, he allows the Anger within him fester to the point where he sees the present world (especially the divided nations that make it up) as an empty and hateful husk that needs to be destroyed, eventually after he awakens as a Newtype and sees that some elements of the world are actually trying to bring their world with the two main combating powers Dark Celestials (as the successful but brutal means) and Terminal (to a less successful but peaceful degree).
Shinn as a Newtype finds he enjoys the killing and absorbing of his enemies' strength to the point that he consumes their rage which accumulates as the source of power which lets his Newtype powers grow, despite getting revenge on Hikari plenty of times it has descended to the point where he doesn't care who is enemies are so long as he is fighting for his personally chosen goal, therefore the rage at Hikari became only a starting point for the Beast of Wrath.
Shinn is still impulsive, stubborn, hot tempered, and sometimes proud even to his superior officers. Shinn has also shown to act on his own feelings, this sometimes put him in odds with his superior officers. His family's death has also left him with anger against his homeland of Orb and the rulers of Orb, the Atthas though he still seems to have some faith in Orb however this is later burned out of him once he becomes a Newtype and understands the larger picture.
Shinn is however surprisingly kind to many people including Rey Za Burrel and Lunamaria Hawk whom are his teammates, after becoming a Newtype he bonds with the "three Druggies" especially Orga Sabnak whom confirms that it was the attacks from the Freedom that killed his parents and the events that put Orga in his position at the First Battle of Orb anyway, early on in Newtype Destiny he falls in love with his Mentor and Superior: Kira Li Creuset whom accepts these feelings and seemingly reciprocates them.