Whatever the plural of the term is, any established player of Diplomacy has such a relationship with another player, spanning the range from simple rivalry to outright dispisement.
Does anyone on the site have a definite nemesis, and if so, who are they and why are they so competitive with you?
For me, it's James Tiberius Kirk
userID=10241 . Ever since I "betrayed" him in year one of my first game he's hated my green guts, so, naturally, I egg him on! =]