That's funny because the Borg style machine empire has been the most powerful build by far for years now.
Most powerful now is lithoid hivemind with terravore trait and calamitic birth origin , when you use the (cheap) colonize option by meteor you create blockers on the new planets, you then spam it everywhere . Clear blockers you get extra pops , consume the planets you get a bit of eveyrting , keep a few central well defended good planets, consume everything. When the planets break , all the pop are automatically relocated . So what was a weaker build turns out a godly build completely bypassing pop troubles. Then of course you spec them for mineral and they have volatile mole traits , to help clearing blockers faster
You now have an economy with colosal mineral production and stock, spam the menace ships they only cost minerals, dont even give a fuck about their fits, you will crush eveyrone under the sheer mass.Huge empty space area so they will never reach your core system . Oh and devouring planets even raise your menace score, star eaters are beasts ...
Wasnt already hard to beat AI, now its just map painting without any challenge, they did absolutely nothing even fallen empire were dwarfed by the strategy before 2400. Even in multi i think if everyone dont immediately rush the crisis or pick crisis too the game is over .
Besides you have the new espionnage system , completely useless requiring ton of micro. In 3.0 its either completely overpowered or completely shit . Unprofessional as fuck , at the 20 euro price tag , a whole brand new indie game , like shadow empires.
Then second to that is indeed the assimilator borg build, or necrophages purifier , they assimilate extremely fast.But do not pick nihilitic acquisition with them, its bugged, the list of bugs and oversights is too long as usual.