Something nuts. A less restricted Skarbrand's sheer rage creates Warp storms. Assuming even below average-sized Warp storms, this is incredibly casual tier 4 stuff.
"Even in his banishment, Skarbrand continues to serve his lord and further the ends of Chaos. He played a crucial role in the shattering of Craftworld Biel-Tan, although unwittingly, and fought a titanic duel with Roboute Guilliman as the Primarch sought to reach Terra. Since the Great Rift, he moves erratically across the galaxy, his sheer fury manifesting terrible warp storms around him."
The Skulltaker is an absolute madman (dae-man?).
"Since his ascension, the Champion of Khorne has carved a bloody path through the millennia. Skulltaker fought alongside the Daemon Primarch Angron on Armageddon, cutting down several Grey Knights Brother-Captains in his infinite wrath. On Agrippina-6, Skulltaker slew the Ork Grimsnag Urk in a titanic duel that lasted a day and a night, the combatants wading through the mutilated corpses of the Warlord's once unstoppable horde. A full score of Aeldari Exarchs fell to his blade during the fighting at Haranshemash, even their prodigious skill and experience falling short of the Herald's. Indeed, every race in the galaxy has its fearful legends concerning Skulltaker and his horrific exploits."
Even Khorne's footsoldiers are ridiculous. Bloodletters:
A) can never be disarmed.
B) insta-kill anyone cut by their blades, as even a minor flesh wound sucks out souls and bleeds a victim dry.
C) grow stronger every single time they kill something.
"Hellblades are carried by the core of Khorne's soldiery ― his Bloodletters and many of his Heralds. Jagged iron swords whose blackened blades glow with the red-hot warp energies of Khorne's domain, each of these weapons is formed from its wielder's own essence, and can never be discarded nor torn from the Daemon's grasp. A mere flesh wound from a hellblade can slay even the most resilient of mortals, as the sword drains their soul and bleeds their corpse dry. Every life taken in such a way fuels the bearer's power and rage, and, having gorged itself on slaughter, a carrier of a hellblade is even more terrifying at a battle's close than its start. Be that as it may, there is never enough carnage to sate the appetite of a Daemon of Khorne, nor that of the god they worship or the blade they wield."
Juggernauts are completely immune to small-arms fire, and only the heaviest weapons have even a chance of punching through their hide.
"Many an aspiring Daemon has leapt upon the back of an enraged Juggernaut, only to be thrown and crushed into an unrecognisable smear. However, once mastered, a Juggernaut becomes the most lethal of all war-mounts. Small arms fire patters harmlessly from its hide, merely serving to enrage the daemonic beast further. Only the heaviest weapons have a chance of piercing its armoured skin, and by the time such armaments are brought to bear, it is usually too late."
A single pack of Bloodcrushers can destroy entire tank companies, level fortresses, and destroy Imperial Knights. A legion of them can lay waste to an entire planet.
"Any brave or foolish enough to stand their ground in the face of this stampede are crushed beneath the pitiless brass hooves of the cavalry of Khorne. Entire Astra Militarum tank companies are as nothing to them. Their wrecking-ball charges have levelled fortresses, flattened Exodite temples and brought down Imperial Knights. While a single pack of Bloodcrushers can annihilate an army, an entire legion of them can decimate a world."