User blog comment:Lune Crackham/Is the Emperor of Mankind really a hero?/@comment-7993663-20170425002100

Well, when Guilliman resurrects (by Cawl and the Ynnari) he regrets to have fought for the achievements the Emperor wanted for Humanity...

But for making that we need to remember that Emperor himself made a deal with the Chaos Gods to grant him power in order to cleanse the Galaxy...

So who knows? Maybe the first corrupted ever was the Emperor himself and the corruption of some of his "sons", the Primarchs, were only another brick in that wall xD