Join Date: Jul 2009
Location: Spixworth, Norwich
Well Horus was laid low by that blade on Davin, and was taken to the 'temple of the snakes'(something along those lines), so I think Chaos was able to corrupt him in his weakened state rather than a genetic flaw. He had his doubts before this thanks to Erebus, which made it even easier for chaos to corrupt.
Fulgrim I don't think would have turned were it not for the Laeran blade. I think he would have destroyed Horus' fleet when he had the chance had he not been handed the Laeran blade just before. So again, I don't think it was a genetic flaw.
Angron on the other hand seemed pretty genetically flawed, because of his personality. He was a mad-man, and then they implanted a 'rage chip' into him on his home planet making him even more bloodthirsty. I think we would have fallen to Khorne no matter what.
Nigh Haunter technically turned renegade before the rest of the Astartes. He wasn't corrupted by chaos I don't think, rather he was just the outcome of his childhood and personality. He might have been corrupted by his visions though.
Overall, I don't think any of the traitors had genetic deffects really. I think it was more of their upbringing, relationship with their fellow primarchs, and chaos corrupting them.
Had they not have been scattered, I don't think many would have turned to chaos, or at least not on the same scale.