Heartwarming / The Roboutian Heresy

• Roboutian Heresy Angron is this full stop. Despite everything, and the changes to canon, he's one of the most compassionate people to exist in universe and in the setting as a whole. Yes, even canon universe. The man makes canon Vulkan look selfish in comparison.
• Unlike his canon self, Lorgar grew to be a far more noble man, who, after learning truth about Covenant on Colchis, spent his life to fight for Imperial Truth in order to protect humanity, especially from Chaos.
• Konrad Curze actually managed to achieve long-lasting, positive change for Nostramo here. Due to his wise rule as king, the once crime-ridden hellhole is now a prosperous trading world and considered the safest place in all the Imperium. The Night Lords are so beloved that it's population will rise up and fight off any Chaos attackers alongside them in the rare event that they somehow slip past the Eight Legion's defenses.
• Perturabo fretting about meeting the Emperor, since he declined to rule Olympia after making it into a paradise because he wanted to retire into the countryside and study engineering... only for the Emperor to fondly declare Perturabo is truly his son, implying He too intended to abdicate once His glorious dream would have been made into a reality.
• Konrad Curze meets his father, and the Emperor (for a time) takes away the pain of his visions. Curze hugged him out of sheer joy.
• The last words of Death Guard chapter. It appears that Mortarion has become the leader of Legion of Damned, meaning even in death, he still serves.
• Magnus' return after his soul was trapped in the Warp for ten thousand years. It's also a Moment of Awesome for everyone who brought it together, especially Ahriman, and Magnus for his big entrance.
• After escaping from the Chaos Gods' prison and getting "the Sword that was Promised", Lorgar had the perfect chance to slay Lion El'Jonson. However, he chose to offer forgiveness and redemption to the Daemon Primarch.
• Most of Ciaphas Cain's part in the Cadian Apocalypse Part 3 stretching from Jurgen's sacrifice and Cain's refusal to fall to Chaos seeing as it would dishonor his sacrifice, all the way to the end where Cain recognizes Ibhram Gaunt never fell to Chaos by choice, and pulled him and the Tanith First And Only free of Chaos's control.
• For all his villainy, Fabius Bile really cares about his daughter, Melusine, and vise versa, to the point he chose to sacrifice his life for her, with expectation he won't return as clone (he did).
• The reason why Sigismund betrayed Dorn? He learned that his gene-father and his legion got bound and used by Guilliman and turned on them in order slowly break Warmaster's hold, thus starting the Blood Crusade for Khorne to seal the deal. All of this was to free his legion from chains of Guilliman.