Frederic-104

Lieutenant, Junior Grade Frederic-104 is a Spartan-II Commando and is one of the few surviving SPARTAN-II. Historically, Frederic-104 has held the highest rank among any of the active Spartan-IIs (n.b. excluding those who were reassigned following failed augmentation, e.g. Fhajad) except for Kurt. He has been known to become greatly affected by his injured teammates. He has also had a close working relationship with John-117. He is now active in the Shield World, but is marked as MIA.

(from Halo Wikia)