Before Fulgrim became the Phoenix Pervert, he was a really good guy.
Primarch Pilgrimage: Perturabo – The Hammer of Olympia by Guy Haley
Another book in which we learn Perturabo is just a bitter man-child.
Primarch Pilgrimage: Ferrus Manus – Gorgon of Medusa by David Guymer
His hands may be iron, but his emotions certainly aren’t as steadfast.