Jureth was a Klingon lord, once heir to the House of Mi'Qogh until he went rogue. He was the older brother of the player. He led the elite forces of the House. He was killed after he initiated the self-destruction sequence when the hull of his Negh'Var-class ship was critically damaged by the player's attacks. (TNG video game: Starfleet Command III)
His starship being the final boss of the Klingon campaign, the best trick to defeating him is to fire at his ship when he cloaks or uncloaks, because his shields are lowered when he cloaks. Even so, you need to fly a Negh'Var-class ship of your own if you are to have any hope of "defeating" him. Because if you engage him while being too close to the asteroid base (similar to the Krolom-792 asteroid base you had to capture much earlier in the game) you get hammered by both Jureth's ship and the asteroid base.
He admits defeat when his HP (hull points) are below 25% and self-destructs at this point.