Knocked out by the Lion

The Lion thought that this was still some kind of honour-duel. They had pummeled one another to the edge of consciousness, demolished half of the Tyrant's palace in their fury, and still the Lord of Angels was demanding satisfaction.
It was madness.
Russ roared out his laughter, throwing his head back against the streaming walls. He forgot it all- the hunt, the Crusade, the sickness in his Legion's soul, the politics of the fraternity of primarchs, the destiny of the species, and rocked in uncontrolled, puerile glee. So he never saw the blow that ended it all.
He never tensed for it, never put up a warding arm, and never even watched for the Lion limping across to him, pulling his bloodied fist back and launching the punch that would crack open his skull and knock him as cold as the tombs of Caliban.

Leman Russ: The Great Wolf pg. 159