The Dacians: Rome\'s Greatest Enemy?

[diegis]

I'd say the Parthians remained at the top, and overall I think it's a Tie between the Sassanid Persians and the Hunnic Empire.

Goths and Vandals probably did more damage overall. They broke the back of the West.

Well, Goths was at least partially Getae/Dacians but they (and Vandals, Huns etc) come later, at the time when Roman empire passed its peak of power (which was reached during the Trajan and the "five good emperors" period) and was heavily affected by the third century crisis, epidemics and especially endless internal strugles for power, economic problems, split of the empire and such