I'm not sure if this is what you're going for, especially as it's something that, at least allegedly, isn't done any more. But when I really want to put a character through prolonged hell (forgive the language), I use slavery. Yes, I'll agree that murder and rape are probably worse (that is, if the slave him/herself isn't constantly raped), but both of those only last a few minutes in general. Slavery is, in my opinion, the most painful chronic condition a human soul can be in. Even just captivity can be, in the long-term, worse than any (relatively) briefer trauma. A really excellent book on this sort of thing, and especially the psychology of the perpetrator/sinner, is The Collector, the author of which I cannot remember.
"In a sort of ghastly simplicity we remove the organ and demand the function...We laugh at honour and are shocked to find traitors in our midst. We castrate and bid the geldings be fruitful." ~C.S. Lewis
Not believing in God after being calmly told about him in an informative manner. No offense to atheist, this is the only answer that follows my beliefs. It is the only unforgiable sin in my beliefs.
Now, If you are looking at this without religious princibles in mind, I would say child abuse and/or see #3
2. What is the worst sin that can be forgiven?
Human trafficking. If you don't know what that is, it means that you are basically keeping a slave. Usually, it is done to immigrants. The trafficker usually charges rent higher then the victim's wages, so they are always in debt, then black out there windows, hide them from visitors, and such. It's cruel and mean.
3. What sin do you think would affect the sinner the most? (emotionally)
Any crime would heavily affect the sinner if they feel sorry for it, but I would have to say committing adultery when you have children with the first husband. The sinner would feel bad for the husband, yes, but the children would put them over the edge.
4. What is the worst sin that you could see yourself committing, and why? (I'm trying to find human vulnerabilities with this one... so, yeah.)
Drunk driving. I'm only 13, but I can see an adult me doing that.
--- Killing another person. As an Atheist - and more accurately, as an Atheist will no belief in any afterlife - for me this is the one life we get. To snuff out another person’s one chance to live is nothing short of terrible. The only exception would be in cases of euthanasia, where oblivion would be preferable to life.
2. What is the worst sin that can be forgiven?
--- Anything can be forgiven. Of course, not all will, nor do they all have to be. But the potential is always there.
3. What sin do you think would affect the sinner the most?
--- I’d imagine this would vary from person to person. Some people are able to feel okay with mass murder … other people (eg. me) feel guilty about killing a bug.
4. What is the worst sin that you could see yourself committing, and why?
--- As I said above, I don’t like even harming bugs. But I’m gonna go ahead and say kill another person anyway. I can’t imagine doing it out of anger or for revenge, but to protect another person/persons that I deem to be worthier to live. I’d be wracked with guilt afterwards though.
