Game-ending random event

  Build fast transports and invade all enemy planets.  The pirates will take care of any defended planets for you.

There is no scaling, it just happens sometimes.

If you go back to the last saved game, it may not even happen again.

The pirate event is horrible, as are many mega events. The mega events are a good idea in theory, but they were poorly implemented and highly exaggerated, making most of them game ending.

Scaling would have a been a really good idea, Stardock...

Ironically, I was playing last night, and just before my final mega invastion the pirates showed up.  I captured the remaining enemy planets in one turn, and the game was over.

This is an equalizing event.  If you get it, you can reload from previous autosave, or choose to play through it.  Say goodbye to all of your ships and starbases - fortified trade routes will survive.  I would sell or scrap every ship immediately.  As mentioned, the only thing you can do is invade planets with fast (or carefully moved) transports.  You could consider upgrade some of your ships to transports that aren't in immediate danger.

Ascertain the pirate's weakness, research/trade techs/logistics/miniaturization to make fleets simultaneously.  In the meantime, don't make any ships at all, unless you have an opportunity to invade with transports.  Otherwise, set miliatart spending to zero.  This may take awhile, but the turns will be fast.  The AI will never recover from this, so its almost an automatic win when you recover.

I seems stupid that the pirates would have such advanced technology in an early phase of the game. What ever happened to scaling? If a civilization has laser technology, then the pirates should have laser technology, not phasor technology!

I had this happen in my current game, and the Pirates promptly sent every race in the game back to the stone age, trapped on their worlds. My medium sized ships, at the time perhaps the strongest in the game, didn't stand a chance. It was dozens of turns biding my time while my new Destroyer fleets were designed and constructed.

The first few versions were wiped out as well, but model after model, my warships started taking more and more Pirate vessels down with them, with the finally victorious design boasting a vast array of shielding and multiple mass driver weapon arrays. The other races have fared even worse, and my new, ever growing Destroyer fleet designed specifically to counter the Pirates now stands uncontested in the galaxy.

I disagree - the mega-pirates are the only event I would categorize this way (well, and the "subspace tear" that limits speed to 5).

The Peacekeepers can be similiar but tend be erratic; they may not work as intended (only attacking ships out of influence borders) but they frequently focus on some races while ignoring others and never seem to totally destroy every ship in the galaxy, the way the pirates do. The Jagged Knife are actually more opportunity then obnoxious, when viewed the right way. The Dread Lords are either a fun challenge or a freebee planet. Most of the others aren't that "mega".

And this is the big problem with the pirates. The point of the mega events was to be unbalancing, but the problem with the mega-pirates is that it's always unbalancing in favor of the player, because the AIs simply can't deal with it. Again the Peacekeepers are similiar but have a smaller effect, and their occasional mysterious habit of totally ignoring a race can swing the game in favor of that AI.