A lesson in inflicting pain

Number one way to make the odds of hurting someone rise exponentially:
bitch about them behind their back.

It would be even more effective if the person in question is a nephew/niece, grandchild, or some other close relation (preferably but not necessarily by blood). If you really want it to hurt, you should arrange for this person to find out from a cousin/sibling or someone of that nature -- someone on their "level" in the family hierarchy.

If you are really bold (or perhaps if the person hasn't actually done anything wrong to bitch about) you could try creating problems and then blaming them on the person, however don't seek the person's help in solving them, this will only give you more ammunition. This will give you a lot to talk about. When talking, try using inventive words to describe the person's (alleged) behaviour such as "whinge".

Guaranteed to work. Or at the very least this will serve to drive a wedge into an already tenuous relationship.

P.S. (Nov 30, 2006): Yes, this is in relation to the Christmas list. There have now been three made: the original (mine), Aunt Agony's and Uncle's (the one who is constantly taking gibes at my walking stick). I wish I was buying for one of them this year so I could get them a lump of coal, however this year I'm buying for Cal. Which is good, cos I actually like Cal and won't have to waste my money on coal.