I guess you could call all top-level players who have often defeated me nemeses, but that isn't really fair. I haven't logged enough games against enough of them for it to count. However, having been ruthlessly destroyed and severely outplayed by Fabian in the DS Championships, I could call him a nemesis, but it was such a graceful annihilation, that it was more respect.
No, my nemeses are those near my level or who once were that I can never seem to get past. I am in the mid-30's now and without numbers to back me up, I believe PSUMVP is the opponent closest in rank who defeats me the most. Perdhapley is higher, but always bests me as well.
I would say WW is to some extent only because I remember the days when we were of equal level. That's right folks, way back when he was in his low-mid 30's, we had a few weeks where we would often play each other. Seeing him become a top player and myself remaining in the those low-mid 30's has always been a bit saddening. Maybe not a nemesis, but a representation of what could have been...