I was playing on a large galaxy with abundant habitable planets and random races. The only winning criteria set for the game is kill everything

I decided to play as Iconian Refugee's
I was being all-evil with any social decisions. I had no military at all but was researching everything and anything by the point this happened I already had finished the hull tree has the best hull building I could in size and all the hull upgrades Q thing researched. I also was about 1/2 way along both the shield tree and the mass driver tree. expert miniaturization
When out of know were The Arceans declare war on me. I think ok. And move money from research into military and design a curser I dubbed Holly Cow MKI It was a huge hull with the following design. 4 nanno rippers and 4 ultimate invulnerability shields. With sensors and two warp engines.
I quick build one and before I can quick build the next one on the next turn. The race I am at war against immediately turn round and say errm this war is not going as we planned. Can we make peace?
Managed to get 3 planets (all 8 or 9’s) out of them and Diplomatic technology from them too with their surrender.