Burx

Burx was a chief warrior in the Horde, who unfortunately was also part of the Burning Blade. Burx had grown up as a slave to humans during the Lethargy of the Orcs, and had been abused by them every day of his life until his liberation by Thrall--Burx, therefore, despised all humans. His prejudice made it easy for the demon Zmodlor to recruit him into the Burning Blade with promises that the cult would try to kill every human on Kalimdor (in reality Zmodlor hoped to cause the humans and orcs to exterminate each other and had recruited many humans into another Burning Blade cult, making similar promises to them about killing all of the orcs).

When Zmodlor's human puppet, Kristoff, found himself on Theramore's throne following the disappearance of Jaina Proudmoore, he ordered Northwatch Hold reinforced, even though a buildup of soldiers at Northwatch would be viewed as an act of aggression by the Horde. Thrall was told of the influx of troops at Northwatch, and Burx (on orders from Zmodlor) convinced Thrall to send him to investigate, and to give him command of an army of at least six hundred. Between them, Zmodlor's two dupes succeeded in starting another conflict between orcs and humans, as when Burx arrived at Northwatch he gave the humans an ultimatum: either dismantle the entire keep and vacate the land in one hour, or be slaughtered.

An hour later, when Burx's terms had not been met, he gave the order to attack. Fortunately for all concerned, Thrall heard what had happened from Jaina and headed for the scene aboard a zeppelin. Once there, he immediately stopped the battle and denounced Burx. Burx angrily protested that he was only acting in the Horde's interest. For his treachery, for consorting with a demon, and after he tried to strike down the human commander with his axe despite the battle being over, Thrall smashed his skull with the Doomhammer on the spot.

Quotes

 * "To wipe out the humans, I'd make a deal with a thousand demons! They gotta be destroyed!" –Last Words
 * "You have brought disgrace to Durotar, Burx. You have caused the dishonorable deaths of orc and troll and human warrior alike. This blight can only be eliminated by your death. As Warchief, it is my solemn duty to carry out that sentence." –Thrall's Final Words to Burx