Sanguinius

Sanguinius, also known as the “Great Angel” and the “Brightest One” during his lifetime, was the Primarch of the Blood Angels Legion of Space Marines. He was killed during the climax of the Horus Heresy at the Battle of Terra defending the Emperor of Mankind from the Warmaster Horus aboard his flagship, the Battle Barge Vengeful Spirit. Though Horus slew Sanguinius, who had once been his closest and greatest friend amongst the other Primarchs, Imperial legend holds that it was the chink in Horus’ armour created by the Angel that allowed the Emperor to slay the Arch-heretic and thus prevent Mankind from falling to the corruption of the Ruinous Powers of Chaos.