I'm going to completely derail this topic and say the worst sin is the abuse of children. Yeah, technically denying Christ, God, and the Holy Ghost after having a perfect knowledge is the worst sin you can commit (according to scripture) but I feel that anyone that knowingly abuses children has done something worse. Anyone that would do that to a child, it just makes me so angry thinking about it. I found out my best friend was abused when she was a child, and I am so angry at the person who did that to her. I haven't ever met the guy, never seen him, but I am so angry at him. I don't know if I'll ever be able to forgive him, even though I either should or don't have to, not sure how it works.
Anyway, that's what I say is the worst. That followed by reality television. Ugh.