Well, if the Spartans get the Chief, it's only fair the Astartes get a named guy too.
Introducing: Lord Kaldor Draigo, Supreme Grand Master of the Grey Knights.
This guy was promoted after his predecessor was killed by Mortarion, a daemon Primarch (basically one of the most powerful daemons that exist, last time one was defeated it took about 100 Grey Knights). His first act of office was to track Mortarion down and carve his predecessors name into his heart. On his own.
Then he got cursed and was trapped in the Warp, Warhammers equivalent of Hell. While there, he:
-Murdered Slaanesh 6 favourite concubines. With his bare hands.
-Killed a Bloodthirster of Khorne and beat the daemon's axe into a new sword for himself, still with his bare hands.
-Burned down the Garden of Nurgle.
-Punched Tzeentch' Inevitable City into rubble, burying one of Tzeentch' most powerful daemons in the process.
He basically pissed off all four gods who rule the Warp. And he's still alive.
By now, the few daemons who do not just flee in terror at his approach are considered crazy and suicidal by the rest. He is not so much trapped in hell..it's more that hell is trapped in with him.
So, Master Chief? Yeah, glhf with that.