III

III has a nice, friendly and gentle demeanor, unlike his brothers' cold and brutal nature. III loves his family a lot and doesn't want them to fight, attempting to mediate disputes between IV and V. Tron stated that III always completed his missions, which are usually important. V trusts III more than he does IV, due to IV's reckless attitude.

Like his brothers, he swears revenge on Dr. Faker, though he cares more about the family's well-being. Though concerned about his family's fate, he also shows concern for his enemies from time to time.

[Spoiler] He is later revealed to be the son of Tron (Byron Arclight) and brother of IV and V, with his real name being Michael Arclight. [/Spoiler]

(Source: Wikia)