I read this chapter again because it's SO GOOD, and now I'm realizing that I'm sure Penelope saying "I hate you a thousand times more than you hate me" in the early chapters suddenly makes sense to him. He may be hurt that some "chimpanzee" took his sister's place and wished she would disappear forever, but HE tormented a girl who was essentially blackmailed into being a substitute but ended up being a punching bag for everyone in that shitty house. He made everyone hate her for a reason she could never really understand because she had no idea about the value of the place she was taken into in the first place.
Penelope is one of the THE best female leads I've ever had the pleasure of reading.
And on an unrelated note, I feel like Penelope is a great example of how point of view can drive a story. Penelope has a mindset of someone who was abused. Everyone is out to get her. So even when characters are being kind, (as we'll see later) she'll assume the worst of them. And that makes sense for her character, but also forces the others seeking her genuine favor to chase after her, thus forcing more interactions, and drives the relationships and the plot further. It's perfect. I love this story deeply, and I can't wait to see the rest of the novel unfold in the manwha.