Custom scenario
Huge map of planet.
All AI permanent pact with each other, vendetta against me, willing to commit attrocities wantonly, with their focus on colony pods and terriformers.
I was limited to 6 cities.
I was doing pretty well up till Lal got the Universal Translator, Secrets of blah blah watch lals dust.
I lost a normal transcend game the other day, myself.
actually, if you play it on trans with only diplomatic victory enabled, it can be pretty difficult if you never really explored that option in the past (a few other limitations on cities, etc would have much more of an impact).