If you were going to kill someone, what weapon would you choose?
A dull knife.
Why a dull knife?
You want to really mess someone up and make it painful? Use a dull knife. Sure, it's going to take a bit more effort, but it isn't going to cut. It's going to rip. It'll be painful, and if they survive the healing process will be a lot more difficult and painful. A dull knife expresses more anger than a sharp knife. A sharp knife is kind of the nice guy murdering tool, but if I'm going to kill someone I'm going to assume that I have finally snapped so I'd go for something painful and vicious.
We've raised a potential serial killer.
I don't know about you, but I'm proud of the amount of thought that went into that.