Cha! You think Clamdiggers or communion-hounds are unstoppable??? Pshaw!
As Alexti (who I think was the one player Norfleet the Unholy expressed respect for) said, you conquer the world quickly enough to not leave the hoarders enough to grow from.
Pythium may be strong in the end game, sure. Then again - I've seen R'lyeh winning from blood magic, and Carrion Woods winning by having more gemic than anyone else. Arcos, at least for me, isn't that strong....
The trick really is to do something they didn't expect : Forge up as an ocean nation, Nexus up as Ulm, etc. You may still lose the game (since most of us lose most of our games, no matter how good we are), but you may help decide who wins.