I don't know.. i find it hard to imagine Dorn or Guilliman or perhaps Sanguinius taking the place of Warmaster and falling to Chaos out of pride or their brothers' jealousy. But then again, its fantasy and lore so making assumptions is pointless Besides, i'd probably say the same about Magnus seeing how he loved his father and was loyal till his world fell apart.
Lion would have been the next best. I don't know much about him but he seems way to rigid. Horus' pride only came out of his feelings of abandonment and the lack of the Emperor's guidance. From what I understand at least. He started questioning the Imperium because the Emperor wasn't there to answer his questions, questions any Warmaster would have run in to. With no answers, he came to his own conclusion. The first HH book made me go from seeing Horus as vain and weak to seeing him as a very dynamic character.
I love the HH books (most of them). It's a great chance to see all the Heresy thing from the other side. So I learned that all the Primarchs who broke with the Emperor, had their personal reasons. Some stupid, some realy dramatically but plausible. You will get a good view of what and why it happens. I personally love the Dark Angel books, because they show the history and the traditions of the Dark Angels in a longer period of time bevor the Heresy happens. Nearly from the beginning, when Lion arrived on Caliban. With that facts it's easier to understand, because Luthor broke with Lion and the Imperium.
Konrad because he was never deluded by glory and stuff, he knew from the beginning what the Emperah wanted from him and what could happen (visionso). Aaaand because his legion rocks.
Konrad because he was never deluded by glory and stuff, he knew from the beginning what the Emperah wanted from him and what could happen (visionso). Aaaand because his legion rocks.
I've only read the first one so you have a lot of information I haven't gotten to. My view of all the primarchs will be changing once I actually get time to read.
I thought a lot about this question a long time ago: which Primarch fits the most to me and my chapter. I'm a follower of ROGAL DORN. He is honest, thoughtful, protective...a real knight. I also like the opinion of Horus: a war between me and Rogal would last forever; the best in attack against the best in protection (or alike). At the zenith of the heresy he had to fortify the Emperor's Palace, great responsibility, great trust in him.
