Lieutenant general
From Halopedia, the Halo wiki
Note: This rank has not yet been mentioned in the Halo Universe.
Lieutenant General is a general-grade commissioned officer rank of the UNSC Marine Corps, UNSC Army, and UNSC Air Force, equal in rank to a Vice Admiral in the UNSC Navy.
In informal settings, Lieutenant Generals are typically referred to simply as "General".
A Lieutenant General may be also referred to as a "three-star General" to distinguish it from the other ranks of General; so named for the three star rank insignia worn on the uniform.