I don't think Abaddon will be more powerful than any daemon primarchs, however a normal Primarch is a different story... Who knows what the gifts of chaos can do, we know they can give a mortal the strength of a SM, but can a SM be as strong as a Primarch?
Additionally wasn't there a thing where Abaddon might be a clone of Horus and was already a giant compared to other SM?
Yeah it has been part of his lore since at least the 2nd edition codex:
In Black Legion, ADB addressed it quite eloquently:
As he floated in the tank, naked of armour and dressed only in a plethora of old scars, that age-old suspicion resurfaced amidst my thoughts. He had always been huge for one of our kind, and had always possessed his primarch’s features, in the way many of the former Sons of Horus tended to do. It was common knowledge even during the Great Crusade that no Space Marine took after their primarch as obviously as Ezekyle Abaddon took after the Warmaster.
But seeing him stripped of battleplate and pretension alike, the similarity between dead father and living son was nothing short of revelatory. I finally gave voice to a question many had considered, yet none had dared ask.
‘Are you Horus?’
His golden eyes glinted with amusement. He dragged in a slow breath through his rebreather.
‘I am Ezekyle Abaddon,’ he said through the medicae tank’s speakers.
‘That is not what I meant.’ I shook my head and gestured to him: this immense figure in the suspension tank, with slabs of muscle over muscle and a demigod-like stature that had led to this legend being whispered throughout the Nine Legions, a legend that would one day be whispered across the galaxy. ‘Are you Horus? Are you his clone? His… son?’
He laughed, the sound wet and tinny over the speakers. ‘What do you believe, Khayon? Do you think I am?’
I saw no reason to lie. ‘Yes.’
This delighted him. I was not sure why.
‘And if I were, brother – if I were merely Horus remade, recrafted, with a twist in my gene-code here and an alteration there, would it change anything?’
I had to think about that. I looked into his eyes but saw no answers there, only amusement.
‘Perhaps. Perhaps you have always been a genetic twin of your primarch. Or perhaps Ezekyle Abaddon was slain in his pilgrimage across the Eye, and you are one of Fabius’ creations in his place. How am I to know?’
This, too, delighted him.
‘So yet again we come back to trust, my brother.’
‘So it seems.’
‘Let me ask you this, Khayon. What does it matter? Clones, sons, fathers… Let the herd whisper whatever truths they choose. Our eyes are set on worthier goals. We look to the future, not the past.’
I acceded with a nod, knowing that there was no answer to be had here. Knowing, ultimately, that he was right. It did not matter.
At least, not if he was on our side.
And in Talon, before this, we have this wonderful nod:
‘The body,’ I said softly.
Falkus knew of what I spoke. ‘They took it.’
Lheor’s laughter was rough across the vox. ‘They didn’t burn it?’
‘They took it.’
The remains of Horus Lupercal – who in time we would come to call the First and False Warmaster – plundered from where they lay in state at the heart of a fortress risen to celebrate his failure.
I exhaled slowly, turning my thoughts to why the Emperor’s Children would plunder his bones. A simple act of desecration? Possible, possible. The III Legion were rarely restrained in such acts of decadence. But this act rang with stronger significance. I could almost hear the warp whisper of it, though the warp can whisper of anything and everything. Only a fool heeds every song it sings.
‘I turned to those I could trust,’ he admitted. ‘Those who have been my allies in the past. You know why they took the Warmaster’s body,’ he said. It wasn’t a question. As long as the Nine Legions had lived in the Eye, there had been whispers of taking the corpse to be used in ways beyond storage in a war museum.
A primarch’s bones... What an offering that would make. What a gift to the powers behind the veil. There was more to this than common theft and decadence.
‘I’m not sure I want to know,’ Lheor muttered. ‘Their idea of ritual desecration is–’
I shook my head, cutting him off. ‘They took it to harvest it. To reap its genetic bounty.’
The Sons of Horus legionary nodded. Cloning wasn’t a word easily spoken by any warrior within the Nine Legions. Even here, in our lawless hell-realm, some sins remained vile. Cloning our kind has rarely worked well. Something in our genetics wracks the process, breeding certain unwelcome instabilities. Cloning a primarch? That was beyond any of us. Probably beyond anyone but the Emperor of Mankind, before his enthronement as a corpse upon his soul engine.
‘They can’t clone Horus,’ said Lheor. ‘No one can.’
‘It’s been done once before,’ Falkus pointed out.
The World Eater gave a piggish snort across the vox. ‘You mean Abaddon? Don’t piss a legend over us and tell me it’s raining truth.’
I allowed him that rather strained wordplay without interrupting. ‘Why would they do it?’ Lheor continued. ‘To what gain? Horus failed once, and he had half of the Imperium marching under his banner. No second chances.’
‘Can you really see no worth in resurrecting the First Primarch?’ Falkus asked.
Edited by Petitioner's City, 10 February 2019 - 09:26 PM.
Cinema itself is a trick of time — still pictures passed through a focused beam of light at 24 frames per second. We are reminded of that in La Jetée...