Defeat Guardian of Orion
Here is a really simple and very lo-tech method of defeating the Guardian of Orion:
1- Design a ship with very little defence and lots of offence. The weapon in the first weapon slot must be able to bring down shields quickly, I usually use Heavy Graviton Beams. The second weapon must be Ion Cannons (Heavy mount if you still don't have version 1.31). Add as many of these as possible (focus more on Graviton beams)
2- Build as many of these as time and resources allow.
3- Go to Orion and kick some butt. Fire all your graviton beams first then use Ion pulse to disable the Guardian, the ideal end result is that you destroy it on your first turn.