This thing is unstoppable when you have all 3 attack upgrades, 4 defense upgrades and a debris vortex upgrade. To help keep itself full of HP after killing everything in sight. My whole plan was to get on a map with a single chokepoint into my territory against 3 teamed unfair AI. I had to really forsake my economy to rush the starbase to the chokepoint, which was a dead asteroid. I batrely had the first 3 defense upgrades and a couple of attack upgrades before the first massive waves of enemy ships attacked.
The key point is to make sure the asteroid stays colonized, and the AI won't move on to your juicy inner worlds. I kept reinforcing it with capital ships, but they were easily destroyed reapeated due to shear mass of vessels. The starbase was mostly unphased. the only thing that can even scratch it were torpedo cruisers. For those I just task all of my fighters and shift click each one. The Starbase was perpetually at zero shields and full health. It never had any time to regenerate shields due to the constant war going on, but the debris vortex kept the hull HP very high. There were a few times when I didn't notice some torpedo cruisers slip in and I got down to 13,000 HP/21,000HP. I was worried but soon after those torpedo ships were dead, my starbase had regenerated on its own.
Because of the massive carnage, I was putting low level capital ships in play and they would instantly level up because of the buffet of experience points in the gravity well. Eventually, the AI fleets got to a point where I feared my starbase couldn't keep up. I was losing lvl 8 carrier caps like they were light frigates, and replacing them without a care, because they level back up so quick. My only fighters were supplied from just 4 hanger defenses and 4 carrier capitals.
The next jump out was a star, i eventually put 4 new starbases out there, but the AI basically ignores them . I upgrades them with colony pods and trade ports to try and help out my suffering economy of only 3 planets.I only had 2 crystal asteroids and I had to buy 95% of my crystal to upgrade.
Once I got enough weapons labs, i upgraded Hull, Armor and Shields and this thing is a total beast. It fears no one. It laughs at torpedo cruisers, slowly flies toward them and crushes them easily. its main weapons do like 240 damage or something, plus like 170 or 180 for its secondary and third weapon systems. 24 armor.
With only 3 planets, my whole economy was based on colony pods and trade port from the starbases on those 3 worlds. I bought resources with my mass of credit income. because I didn't have the logistics to make trade structures, all of my logistics were tied up with weapons and empire labs.
Still, 3 Unfair AIs could not defeat me. Try it.