He's punishing her for having had it better than he did and he justifies his actions with the fact that she did benefit from her bloodline's cruelty and corruption. I sympathise where he's coming from because fuck the monarchy, the power should be with the people, but I think he's also punishing himself for having been in love with her. He knows her guilt ends with her ignorance, and maybe being the daughter of her sworn enemy, so he tied himself down with the reminder of how far he's come and all of his sacrifices.
He built this image of her in her head where she'd be too helpless yet cowardice to proceed with killing herself, but she's faced everything that's thrown towards her with grace and understanding that a spoiled rich girl like her shouldn't have been able to. She doesn't even resent him!
All in all i love this, i almost didn't start reading it because of the title (lol) but it's so refreshing to see something like this. The characters are interesting and very complex and I love anette so much, i honestly don't know what heiner was expecting after driving her into a corner, but i wish the narrative frees them of all their burdens because this already made me cry.
My chest started to feel tight at one point this shit hurts ;_;
Calling her his outcome and his reason pretty much sums up his motivations, he doesn't find pleasure in putting her through this shit, he just thinks she deserves it but we can see it pains him too. Maybe this is his own way of repentance for being in love with her. He's kinda like saying you're a bad person but i'm worse because i want you so i'll suffer with you.