Reservist / Artillerist is surprisingly painful. Thousands of extremely long range ships popping into existence the second you enter most systems on the map...
Overreactive / Mime is another combination I almost regret playing.
But overall, I think Kahuna has it right - One-way Doormaster / Raid Engine is the worst non-Technologist combo I can think of. You can't go anywhere, and when you try you get constant AI fleets attacking, and the AIP is always through the roof, and it all just keeps building up and up and up...
Of course, for unwinnable, just try a Technologist with alt-Champ Nemesis on 10/10.