Well, the AI seems unable to cope well with late game situations, as a general rule.
Actually, let me be a bit more general myself. The AI seems to be optimized for a game that is in the middle in all respects. That is, just as a gauge reads best in the middle of the display range so, too, does the AI seem to do best with all conditions in mid-range, whether it be early or mid-game or late, or small or medium or immense galaxy, etc.
In the larger galaxies, especially abundant ones, the AI does not seem to properly prioritize colonization choices.
With research victory turned off, the AI does not know to build over research buildings when the researching phase is done.
When wars get big, the AI has poor operational behavior, letting the human take planets with their defenders fighting one-at-a-time. A human can create defensive fleets and could even park them at the nexi of multiple speed-assist equipped starbases.
I do not say this game needs multiplayer capability to be a good game. What I do say, though, is that to have a tough opponent under all conditions, there is still no substitute for playing other humans.
I have won at Suicidal several times now, and using 3 different strategies, butonly in the largest galaxies with research victory tunrned off. I have not been able to win Suicidal yet in a medium galaxy, with all victory conditions enabled, max AIs. The game is faster, the AIs beat me down the research trees, they transition out of Colony Rush and into war faster, etc.