Necron Lord of Kronus
The Necron Lord of Kronus is a Necron Lord notable for three things: He's in charge of the Necrons on Kronus, he's one of the most hilariously overpowered things in the entire campaign mode that isn't Gorgutz 'Ead 'Unter, and he does not speak. The Necrons in Dawn of War: Dark Crusade get around this lack of a voice by appointing a Necron Pariah, former human Tomas Macabee (reference to "Macabe" or "Macabre", old rural word for corpse), to act as its herald and mouthpiece on operations. Ages ago, the Necrons swept this world clean of life, and soon, they will do so again if the Necron Lord has his way.
As a servant of the Nightbringer, his goal is embarrassingly simple and yet outright terrifying: the extermination of all life on Kronus. While he does not talk, Relic somehow managed to give him hints of actual personality - most notable during the assault on Eliphas' stronghold, where he manages to successfully unnerve even the Word Bearers champion. While it's never revealed what it is he actually says to Eliphas beyond electronic hissing, Eliphas' response is one of revulsion. The implication is that, as an early-edition Necron Lord, he is utterly beholden to the C'tan, serving the entity as a Lovecraftian entity in an almost religious fashion by sating its hunger for life itself.
The Necron Lord of Kronus engaged in fierce fighting against the Eldar under Taldeer and the Tau under Shas'O Kais, with his forces murdering thousands in their advance. Unfortunately for him, the Blood Ravens under Davian Thule managed to perform a surgical strike, sneaking into the tomb complex and planting a plasma bomb in the center of the tomb complex, causing a massive series of cave-ins and destroying the Necrons on Kronus entirely. So powerful was the bomb that it reduced the area around the complex to a scorched desert.
If the player chooses to play as the Necrons, the Necron Lord of Kronus ultimately fully restores the tombs of Kronus, destroys all life on the planet, and begins sending forces to besiege the Tau Empire, Ultramarines, and Imperial Guard, the Necron Lord of Kronus gradually turning the planet into a blight at the heart of Segmentum Ultima, gradually bleeding the region white to feed the Nightbringer's bloody tally.
Borderline game-breaking when maxed, the Necron Lord of Kronus is arguably the most powerful hero in the campaign. Only Gorgutz (from either Dark Crusade or Soulstorm) is tougher, and while Eliphas, and Carron could wreck him in close combat, none of them have the ability to match up to the Necron Lord of Kronus' gigantic arsenal of abilities.
Unlike the other Dark Crusade campaign heroes, the Kronus Necron Lord starts the campaign almost as powerful as his multiplayer version, with the only difference being that he isn't as good at smashing up buildings. This means that the upgrades he has more freedom in choosing wargear options early on, when it matters most. What makes him terrifying, however, is how well his wargear meshes with his artifact abilities. Heart of Darkness paired with either Phylactery or Phase Shift gives him insane regeneration (even crazier with both), and Death Shroud paired with the same make him take chip damage from most ranged attacks. When fully equipped, he's almost unstoppable, and seeing him solo an enemy base late-game isn't unheard of, especially with Essence of the Nightbringer.
Compared to the Necron Lord of All Kaurava, the Necron Lord of Kronus is tougher, but notably less damaging and worse at breaking morale. However, this doesn't make him any less of a monster when maxed out.