Everyone in this series is so ridiculously overblown that there's not even really any kind of moral dilemma, is there? No one is asking "is it actually a good thing that the child rapist got sent to hell?" and the Mom isn't going to say "wait, why did you kill my abusive, psychopath husband?!"
So just get it over with. This pointless melodrama doesn't elevate the story. It makes it tedious.
I wouldn't call it melodrama. As you say, this series is quite black and white, though as I said in chapter six, a garden variety bully and motorised mugger isn't on the same level as an animal torturer and a rapist, so we're already in greyish territory. As I see it, this series is part revenge porn (enjoying abusive people being sent to hell), part a demonstration of how exactly the road to hell is paved with good intentions. So I don't think there's much room for nuance here.
But Raika's train of thought looks legit to me. He isn't conflicted about sending his sperm donor to hell, he's conflicted about stealing the key from Asura to do it. He's trying desperately to disprove his father about apples falling from trees, so I can't see him actually using physical coercion on Asura to get the key. He's just a cornered middle school kid, I don't think what he's doing is nonsensical.