Most "powerful" house (within RP)

[Ceoran]

In a 1vs1 against any other of the current houses I'd give Kusari the best chances to win.
Why? Their economy is stable and not depending on foreign influence, so they can barely be harmed that way. Certain groups there would even be happy if Libertys attempt to enter the Kusari market would end.
Their inner political situation is special, but the most stable I think. The Dragons are good warriors, but not that many in numbers while the GC are a bunch of female fanatics. They lack the military training many ex-KNF pilots have experienced before joining the Dragons.

Considering Gallia I'd say they aren't ready yet to take on all four houses, otherwise they would have opened the minefields themselves and not the Council. Their technology is the most advanced, agreed, but they can't field a full blow against any house thanks to the Council. With the current inner situation I think Gallia would lose against any house, if they weren't already at war with each other. Without the council I'm sure the Royals could take on each of the houses. With the combined forces of both the Royals and the Council they would even be able to crush two houses at once.
Winning against 3 is unlikely as this would most likely be against a united front of Kusari and Bretonia veterans supplied from an ally whose systems can't be directly attacked.

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