I played an all-abundant game on a medium size map as Altarian. I had my small edge of the universe and kept to myself most of the time. My goal: Win a peaceful tech victory.
I had the tech lead and an overwhelming economy thanks to an economy mining resource I got early. Everything went well, I managed to build every single trade-good and galactic achievement available to me before any AI.
I had been sitting in the north corner of the map, with the Torians to the southeast and the Krynn to the southwest. Between both, most mining resources where concentrated, though I only managed to get the one economy resource (I want to have know-it-all constructors to). In the south, the Korath did their thing.
Lucky for me, the Krynn later declared war on the Torians and a couple of turns later, I had plenty of new starbases.
I gained 2 morale, 3 military and 2 research resources.
I thought everything went well, but before I could maximize the number of mining modules in the new bases, something bad happened.
The Jagged Alliance event. Of my 12 planets, I lost 8, including all trade-goods and galactic achievements.
My economy was ruined, my morale in the cellar and my ship designs useless (lost Hyperion Shrinker).
At least I had 40k BC, used it to rush-buy transports. Immediately I declared war on the Jagged Alliance and started invading.
The problem: They had Tir-Quan training, Harmony Crystals and Frictionless Crystals now, cheering and dancing super soldiers.
100% approval, so I couldn't use information warfare. And I didn't want to improvements to get destroyed or worse, quality drop of the planet, so I had to use traditional warfare.
A painful task, billions of brave soldiers lost their lives. But after a I got some planets back, it got easier. I got my Tir-Quan back and later the morale improving trade-goods.
Slowly my economy recovered as my people breeded and populated the liberated planets.
But I didn't stop after getting my planets back, I sent my transports all over the map. Wherever there was a JA planet, a transporter was already on its way, till eventually I had wiped them out.
Meanwhile, the Torians were defeated by the Korath. They surrendered their last planets to me. I quickly claimed the abandoned influence resource.
And then the chain-reaction started. With the former JA and Torian planets scattered all over the galaxy, deep in enemy territory, my influence skyrocketed, planets started to flip. Realizing that an influence victory was inevitable, I then researched some influence enhancing technologies to reach it faster.
Summary: YAIV (Yet Another Influence Victory) caused by a fun twist, namely the JA event.