Cardassians (Tribunal)would be bad, of course being a Klingon prisoner they would keep telling you that your execution date would be tomorrow and tomorrow it would be next week and the day after it would be tomorrow, Klingons like screwing with their prisoners. (In the Pale Moonlight)
Dominion..... No idea depends on what you have done I guess, but they would either kill you quickly or keep you around for information, I see the Romulans behaving like the shapeshifters on that one as well.
No one mentioned the Kazon yet.... Bunch of low rent Delta quadrant Klingons that bunch is.....
Being a prisoner of the Q would be interesting to say the least