Sorry about the lateness of the reply here.
Well, this is a tricky question. I suppose it hinges on how you define power. If power is simply the number/caliber of guns, then at present I would say it's a tie between the Chaw'Sah'Voh class man'o'war and the Zer'Sees class charlatan. The Chaw'Sah'Voh (seen above) sports 256 wormhole spinners, making her above and beyond the most heavily armed warship presently existing for the Ascendancy in terms of "conventional" firepower. She's had limited use in the scenario thus far, and none as yet where she's gotten into the slug-it-out sort of engagement I designed her for.
Alternatively, the Zer'Sees class commodorehorton.deviantart.com… smaller and sports less wormhole spinners (72 spinners compared to 256) but the Zer'Sees is built around a directed variation of the Flux's tier three superweapon the FSEMCE (commodorehorton.deviantart.com…) which by its nature literally kills everything it's directed at. The Zer'Sees though has not seen any appearances in the storyline thus far though, as at present I'm treating it like some of those 44-45 era Lufwaffe designs that were brilliant but didn't have much in terms of numbers.
Finally, if we're defining strength as simply strength, and not in terms of military power, then it's undeniably the Hands of God class planetary transport (commodorehorton.deviantart.com…) as it drags around planets and is as large as a gas giant. However these guys are unarmed, so military wise they're not really strong beyond the ungodly amount of force required to destroy them.
As I said, it's a tricky question. Normally I would be inclined to agree with you that simply by numbers the Chaw'Sah'Voh has the most guns and is thus the most potent, but the things I put together I put together in a way to try and play with statistics as it were. I dunno. I haven't even fielded the Zer'Sees yet, and created it specifically in response to events in the RP which are presently unfolding. So ultimately it's in my opinion a rather untested question: only time will really tell.