Bero 'Kusovai
From Halopedia, the Halo wiki
Special Operations Sub-Commander Kusovai is an Elite character first introduced in the Halo Graphic Novel. He was known for his skill with the Energy Sword.
In context
Kusovai is first seen in a practice duel with Rtas 'Vadumee. Later, he is with the group that boards the Infinite Succor and realizes that something is amiss. When they head into a hunting preserve there are Flood infested animals that begin attacking the group. The group fights its way through to the ship's bridge, where they find the controls have been disabled.
Kusovai is eventually absorbed by the Flood and fights Rtas, costing the latter part of his jaw. The Flood are almost able to Slipspace jump out of the system but not before Rtas changes the course to slipspace into the sun. It was here that Rtas, while fighting an infected 'Kusovai, is injured as an Energy Sword cuts off his left mandible. Rtas defeats 'Kusovai and manages to escape two minutes before the Slipspace Jump occured. Rtas is believed to be the only survivor of the Infinite Succor mission.
Rank
His true rank is unknown, although he must have been lower ranked than Rtas 'Vadumee, but higher than normal Special Operations Elites. Most believable is that he was Special Operations Officer (also called Spec Ops Major), as Zuka 'Zamamee, but he could even be an Ultra Elite with the role as Sub-Commander.
Name
Kusovai's naming structure is odd, as he has neither the apostrophe before the last name nor the "-ee" suffix common to military Elites. However, given his mastery of the energy sword, it seems foolish to conclude that he is a civilian. More likely, it is an oversight, error, or piece of artistic license on the author's part.