I'd say he felt guilty about both at the time, so I don't see how it's so apparent. He felt "like an utter bastard for asking" Molly to do it. I can't think of a quote precise enough to easily search, but I'm pretty sure he felt guilty for bringing all his friends with him, Molly most specifically, at the time.
He did feel guilty, he always has, that is why he tries to keep so much from his friends, but they volunteer anyway. Actually I believe he tried to talk Molly out of
coming with them, she insisted. Again, she was young, but not a child by any means and under no illusions that it would be a cake walk.
The only reason I was focusing on the lie is that Mira disputes that it was a lie. Lying is wrong, but it's wrong like killing people is wrong. Sometimes, it's actually the right thing to do because we live in an imperfect world. (Obviously killing is on a very different end of the moral gravity spectrum).
Yes, it is an imperfect world, and like what Mab says about death, there is a spectrum to it, not black and white. What I objected to is the idea and perhaps I misunderstood you, that because Harry had told Susan that the knife wouldn't hurt her to get her to attack, he murdered her. I'm saying it isn't that simple, nor how it went down. Go back to when they started their journey it was Lea that made a show about Susan's cloak and skin protecting her, that was the original lie, but then the Fae supposedly cannot lie. Harry should have objected then, and he did actually, by saying he'd rather wear Kevlar, then Lea shot a bullet at Susan and it bounced off. That complicates things, Harry was repeating basically what Lea had said and demonstrated, though he didn't believe it himself, outright lie or something he couldn't prove? Why did he say it? My belief is he was trying to calm her so she'd think, for that brief time if she believed what Lea had said she'd be less afraid.. When she calmed down, thought back, then she could ask the questions of Martin that needed to be asked,
that is when the truth came out. That is when she decided to attack, not the Red King who had the knife and was headed for the alter to cut their daughter's throat, but Martin. Once Susan attacked Martin and began to turn, that is when it all hit the fan. Actually that had been Martin's plan all along, sacrifice himself and Susan so that Harry could bring the Red Court down.. So who was the real manipulator here? It wasn't about Susan being afraid or not that the knife could hurt her, she never attacked the one who had it and was actually moving towards their daughter in that moment to cut her throat. So nasty black lie told deliberately to get Susan to attack ergo getting her murdered? Not exactly.
If Harry had told Susan that Lea was wrong about a steel knife not hurting her, would that have changed things for the better? If he had said nothing about the knife, would it have been a lie by omission? Nano seconds count, Harry needed Susan's brain to focus to save them all.. If it was a lie it was the whitest of lies told for the best of reasons.. Yes, even when it comes to morality, there is a spectrum to it, it isn't always black and white.