I've had the game for a week, and I've had a chance to play a couple rounds against different random opponents.  I'm trying to knock out the accomplishments of beating 2, 3, & 4 Hard oppenents single-handedly, then more opponents if possible.  What do you think the easiest opponent configurations would be?  I tried a round yesterday against a couple economist AI Advent opponents, and it was pretty tame.  Has anyone found researcher/defender/etc to be easier?  Likewise, which ones prove to be the hardest?