I actually felt pity for Dussander up until these last few pages. I genuinely thought that he felt remorse for his war crimes and that Todd was simply forcing him to relive them. But now I realize he gets a sick pleasure out of killing, and kills stray cats in his oven for fun/to alleviate his nightmares. He's even considering upping the ante to dogs. It makes me sincerely doubt that he ever felt any remorse for all of the people he killed in the concentration camps, despite what his actions at the beginning of the story seemed to indicate. Or maybe he convinced himself that he did feel remorse, and Todd is bringing out the evil man he once was by making him relive his time operating the camp. Both he and Todd are equally despicable and make me sick.
Todd makes me sick on a different level. He's a spoiled, entitled little brat who thinks he can control an old man by threatening to reveal said man's past. He extorts stories out of Dussander, makes him dress up in a replica of an SS uniform, and forces him to relive the goriest moments of his past. Todd could be partially responsible for Dussander's lapse back into killing - even if the victims are only stray cats - because if he hadn't confronted Dussander about his true identity and dragged the lurid stories out of him. Before Todd, Dussander was living a lonely but nightmareless life.
Now, Todd's grades are slipping and he's blaming it on Dussander and his stories - the stories that Todd has been extorting from him, stories Dussander didn't want to revisit. He's demanding that Dussander help him fix his grades because the stories are all he can think about and causing him nightmares - therefore his failing grades are Dussander's fault, and Dussander must fix them.
Seriously, you're an evil, manipulative little shit, and I want to wring your neck.