Hm.. In a live tournament with a normal time control and talking rating, not real "strength" wise, I guess it had to be GM Aloyzas Kveinys, who was rated around 2546 at that time. Have beaten 4 or 5 other GM's, but I think they were all lower rated that Kveinys. Drew a couple too, strongest of them probably was GM Markos who was 2565 at that time. And then somewhere around 20 (that's from the top of the head, might be +- some) wins agains IM's of all strength (some really weak, like old guys with 2250, who used to be decent IM's). If we count online.. Well, the list is far bigger