If you're talking about what I think you are, the system Uvas, in addition to what Hatter already said:
If you can't build a flagship beefy enough to solo this fight, I had luck building the other ships to be extremely tough but not to present a threat to my flagship. If you load out disposable cruisers and battleships (and they WILL die gratuitously, this thing makes the Hypershunt fight look like Spongebob) with either all beam loadouts or all light kinetic loadouts, they will be mostly harmless to your flagship's shields or armor if when they get mind-controlled. It's not particularly tough once you corner it, it's just keeping up with it while weathering its storms of lightning and purple Itano Circus nonsense. As your other ships get controlled, place Avoid orders on them and keep ordering your friendly ships to focus on the boss. Once you beat that cosmic horror, you get it with its crazy powers intact. Good hunting!
