[dogscoff]

You are bread, they are gravy.

If you've hit MEE, then you're powerful enough to attack those remaining empires, crush their fleets, sweep aside their defences, conquer their planets and have their humbled leaders dragged in shackles before your throne. Oh, and you should start work on a Ringworld or two, just to pass the time.

That's the best way to 'end the union.'