Lojur

From Memory Alpha, the free Star Trek reference

Lieutenant Commander Lojur was a 23rd century Starfleet officer of Russian descent, who served as the helmsman aboard the USS Excelsior under Captain Hikaru Sulu.

Lojur served at the helm aboard the Excelsior during its three-year mission cataloging gaseous planetary bodies in the Beta Quadrant, from 2290 to 2293. He also served at the helm during the battle at Khitomer against Klingon General Chang in late-2293. (Star Trek VI: The Undiscovered Country; VOY: "Flashback")

Lojur was played by actor Boris Lee Krutonog. It should be noted that his accent was far thicker in "Flashback" than in STVI. Some novels stated that Lojur was actually Halkan in origin. That seems rather odd since Halkans disliked any form of violence and presumably would encounter it in Starfleet. In some of these novels, however, it is said that Lojur is the only one of his race to feel any violent emotions, which would seem to compensate.